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‎README.md

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# 数据结构与算法分析 Java语言描述
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书中代码以及课后习题。

‎data-struct-java.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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</component>
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</module>

‎src/ch02/MaxSubSum.java

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package ch02;
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import java.util.ArrayList;
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import java.util.LinkedList;
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/**
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* Created by cookfront on 2017/2/14.
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*/
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public class MaxSubSum {
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public static void main(String ...args) {
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int[] subs = {-2, 11, -4, 13, -5, -2};
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System.out.println(maxSubSum1(subs));
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System.out.println(maxSubSum2(subs));
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System.out.println(maxSubSum4(subs));
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}
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public static int maxSubSum1(int[] arr) {
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int maxSum = 0;
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for (int i = 0; i < arr.length; i++) {
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for (int j = i; j < arr.length; j++) {
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int thisSum = 0;
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for (int k = i; k <= j; k++) {
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thisSum += arr[k];
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}
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if (thisSum > maxSum) {
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maxSum = thisSum;
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}
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}
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}
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return maxSum;
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}
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public static int maxSubSum2(int[] arr) {
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int maxSum = 0;
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for (int i = 0; i < arr.length; i++) {
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int thisSum = 0;
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for (int j = i; j < arr.length; j++) {
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thisSum += arr[j];
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if (thisSum > maxSum) {
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maxSum = thisSum;
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}
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}
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}
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return maxSum;
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}
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public static int maxSumRec(int[] arr, int left, int right) {
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if (left == right) {
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if (arr[left] > 0) {
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return arr[left];
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} else {
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return 0;
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}
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}
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int center = (left + right / 2);
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int maxLeftSum = maxSumRec(arr, left, center);
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int maxRightSum = maxSumRec(arr, center + 1, right);
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int maxLeftBorderSum = 0;
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int leftBorderSum = 0;
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for (int i = center; i >= left; i--) {
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leftBorderSum += arr[i];
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if (leftBorderSum > maxLeftBorderSum) {
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maxLeftBorderSum = leftBorderSum;
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}
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}
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int maxRightBorderSum = 0;
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int rightBorderSum = 0;
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for (int i = center + 1; i <= right; i++) {
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rightBorderSum += arr[i];
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if (rightBorderSum > maxRightBorderSum) {
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maxRightBorderSum = rightBorderSum;
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}
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}
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return max3(maxLeftSum, maxRightSum, maxLeftBorderSum + maxRightBorderSum);
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}
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public static int max3(int a, int b, int c) {
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if (a > b && a > c) {
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return a;
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} else if (b > a && b > c) {
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return b;
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} else if (c > a && c > b) {
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return c;
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}
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return Integer.MIN_VALUE;
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}
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public static int maxSubSum3(int[] arr) {
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return maxSumRec(arr, 0, arr.length - 1);
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}
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public static int maxSubSum4(int[] arr) {
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int maxSum = 0;
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int thisSum = 0;
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for (int i = 0; i < arr.length; i++) {
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thisSum += arr[i];
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if (thisSum > maxSum) {
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maxSum = thisSum;
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} else if (thisSum < 0) {
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thisSum = 0;
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}
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}
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return maxSum;
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}
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}

‎src/ch03/MyArrayList.java

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package ch03;
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import java.lang.Iterable;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* Created by cookfront on 2017/2/20.
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*/
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public class MyArrayList<AnyType> implements Iterable<AnyType> {
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private static final int DEFAULT_CAPACITY = 10;
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private int theSize;
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private AnyType[] theItems;
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public MyArrayList() {
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doClear();
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}
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public void clean() {
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doClear();
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}
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private void doClear() {
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theSize = 0;
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ensureCapacity(DEFAULT_CAPACITY);
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}
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public int size() {
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return theSize;
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}
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public boolean isEmpty() {
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return size() == 0;
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}
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public void trimToSize() {
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ensureCapacity(size());
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}
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public AnyType get(int index) {
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if (index < 0 || index >= size()) {
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throw new ArrayIndexOutOfBoundsException();
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}
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return theItems[index];
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}
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public AnyType set(int index, AnyType newVal) {
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if (index < 0 || index >= size()) {
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throw new ArrayIndexOutOfBoundsException();
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}
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AnyType old = theItems[index];
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theItems[index] = newVal;
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return old;
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}
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public void ensureCapacity(int newCapacity) {
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if (newCapacity < theSize) {
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return;
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}
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AnyType[] old = theItems;
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theItems = (AnyType []) new Object[newCapacity];
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for (int i = 0; i < size(); i++) {
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theItems[i] = old[i];
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}
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}
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public boolean add(AnyType val) {
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add(size(), val);
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return true;
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}
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public void add(int index, AnyType val) {
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if (theItems.length == size()) {
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ensureCapacity(size() * 2 + 1);
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}
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for (int i = theSize; i > index; i--) {
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theItems[i] = theItems[i - 1];
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}
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theItems[index] = val;
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theSize++;
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}
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public AnyType remove(int index) {
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AnyType removedItem = theItems[index];
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for (int i = index; i < size() - 1; i++) {
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theItems[i] = theItems[i + 1];
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}
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return removedItem;
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}
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public Iterator<AnyType> iterator() {
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return new ArrayListIterator();
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}
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private class ArrayListIterator implements Iterator<AnyType> {
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private int current = 0;
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public boolean hasNext() {
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return current < size();
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}
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public AnyType next() {
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if (!hasNext()) {
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throw new NoSuchElementException();
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}
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return theItems[current++];
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}
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public void remove() {
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MyArrayList.this.remove(--current);
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}
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}
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}

‎src/ch03/MyArrayQueue.java

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package ch03;
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import java.lang.Iterable;
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import java.util.Iterator;
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/**
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* Created by cookfront on 2017/3/2.
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*
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* 数组实现的队列
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*/
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public class MyArrayQueue<AnyType> implements Iterable<AnyType> {
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private static final int DEFAULT_CAPACITY = 10;
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private int topOfStack;
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private AnyType[] theItems;
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private int theSize;
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public MyArrayQueue() {
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doClear();
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}
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private void doClear() {
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theSize = 0;
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topOfStack = -1;
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ensureCapacity(DEFAULT_CAPACITY);
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}
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public int size() {
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return theSize;
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}
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public boolean isEmpty() {
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return theSize == 0;
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}
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public void push(AnyType val) {
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if (theItems.length == size()) {
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ensureCapacity(size() * 2 + 1);
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}
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theItems[++topOfStack] = val;
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}
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public AnyType pop() {
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return theItems[--topOfStack];
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}
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public void ensureCapacity(int newCapacity) {
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if (newCapacity < theSize) {
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return;
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}
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AnyType[] old = theItems;
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theItems = (AnyType []) new Object[newCapacity];
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for (int i = 0; i < size(); i++) {
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theItems[i] = old[i];
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}
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}
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public Iterator<AnyType> iterator() {
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return new ArrayQueueIterator();
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}
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private class ArrayQueueIterator implements Iterator<AnyType> {
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@Override
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public boolean hasNext() {
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return false;
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}
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@Override
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public AnyType next() {
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return null;
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}
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}
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}

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