Solve section6

Author: dmakwt

problem-solving-patterns/anagram_2_frequency_2.js

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+const validAnagram = (str1, str2) => {
+  const freq1 = {};
+  const freq2 = {};
+
+  for (let letter of str1) {
+    freq1[letter] = (freq1[letter] || 0) + 1;
+  }
+
+  for (let letter of str2) {
+    freq2[letter] = (freq2[letter] || 0) + 1;
+  }
+
+  for (let key in freq1) {
+    if (!(key in freq2)) {
+      return false;
+    }
+
+    if (freq1[key] !== freq2[key]) {
+      return false;
+    }
+  }
+
+  return true;
+};
+
+console.log(validAnagram('true', 'turee'));

problem-solving-patterns/countUniqueValues.js

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+const countUniqueValues = (arr) => {
+  let i = 0;
+  let j = 1;
+
+  if (arr.length === 0) {
+    return 0;
+  }
+
+  while (j < arr.length) {
+    if (arr[i] !== arr[j]) {
+      i++;
+      arr[i] = arr[j];
+    }
+
+    j++;
+  }
+  console.log(i + 1);
+
+  return i + 1;
+};
+
+countUniqueValues([1, 1, 1, 1, 1, 2]); // 2
+countUniqueValues([1, 2, 3, 4, 4, 4, 7, 7, 12, 12, 13]); // 7
+countUniqueValues([]); // 0
+countUniqueValues([-2, -1, -1, 0, 1]);

problem-solving-patterns/max_sum_naive.js

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+function maxSubarraySum(arr, num) {
+  if ( num > arr.length){
+    return null;
+  }
+  var max = -Infinity;
+  for (let i = 0; i < arr.length - num + 1; i ++){
+    temp = 0;
+    for (let j = 0; j < num; j++){
+      temp += arr[i + j];
+    }
+    if (temp > max) {
+      max = temp;
+    }
+  }
+  return max;
+}
+
+maxSubarraySum([2,6,9,2,1,8,5,6,3],3)
+
+

problem-solving-patterns/max_sum_refactored.js

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+function maxSubarraySum(arr, num) {
+  let maxSum = 0;
+  let tempSum = 0;
+  if (arr.length < num) return null;
+
+  for (let i = 0; i < num; i++) {
+    maxSum += arr[i];
+  }
+
+  tempSum = maxSum;
+
+  for (let i = num; i < arr.length; i++) {
+    tempSum = tempSum - arr[i - num] + arr[i];
+    maxSum = Math.max(maxSum, tempSum);
+  }
+
+  return maxSum;
+}
+
+console.log(maxSubarraySum([2, 6, 9, 2, 1, 8, 5, 6, 3], 3));

problem-solving-patterns/unique_values.js

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+function countUniqueValues(arr){
+    if(arr.length === 0) return 0;
+    var i = 0;
+    for(var j = 1; j < arr.length; j++){
+        if(arr[i] !== arr[j]){
+            i++;
+            arr[i] = arr[j]
+        }
+    }
+    return i + 1;
+}
+countUniqueValues([1,2,2,5,7,7,99])

section6/areThereDuplicates.js

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+const areThereDuplicates = (...array) => {
+  const freq1 = {};
+
+  for (let val of array) {
+    freq1[val] = (freq1[val] || 0) + 1;
+  }
+
+  for (let key in freq1) {
+    if (freq1[key] > 1) {
+      return true;
+    }
+  }
+
+  return false;
+};
+
+console.log(areThereDuplicates('a', 'b', 'c', 'a'));

section6/averagePair.js

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+const averagePair = (arr, num) => {
+  let start = 0;
+  let end = arr.length - 1;
+
+  while (start < end) {
+    let avg = (arr[start] + arr[end]) / 2;
+    if (avg === num) {
+      return true;
+    } else if (avg < num) {
+      start++;
+    } else {
+      end--;
+    }
+  }
+
+  return false;
+};
+
+console.log(averagePair([1, 2, 3], 2.5));
+// console.log(averagePair([1, 3, 3, 5, 6, 7, 10, 12, 19], 8));

section6/findLongestSubstring.js

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+const findLongestSubstring = (str) => {
+  let longest = 0;
+  let seen = {};
+  let start = 0;
+
+  for (let i = 0; i < str.length; i++) {
+    let char = str[i];
+    if (seen[char]) {
+      start = Math.max(start, seen[char]);
+    }
+    // index - beginning of substring + 1 (to include current in count)
+    longest = Math.max(longest, i - start + 1);
+    // store the index of the next char so as to not double count
+    seen[char] = i + 1;
+  }
+  return longest;
+};
+
+console.log(findLongestSubstring('bbbbbb'));

section6/isSubsequence.js

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+const isSubsequence = (str1, str2) => {
+  let i = 0;
+  let j = 0;
+
+  if (!str1) return true;
+
+  while (j < str2.length) {
+    if (str1[i] === str2[j]) {
+      i++;
+    }
+
+    if (i === str1.length) {
+      return true;
+    }
+
+    j++;
+  }
+
+  return false;
+};
+
+console.log(isSubsequence('abc', 'acb'));

section6/maxSubarraySum.js

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+const maxSubarraySum = (arr, num) => {
+  let maxSum = 0;
+  let tempSum = 0;
+
+  if (num > arr.length) {
+    return null;
+  }
+
+  for (let i = 0; i < num; i++) {
+    maxSum += arr[i];
+  }
+
+  tempSum = maxSum;
+
+  for (let i = num; i < arr.length; i++) {
+    tempSum = tempSum - arr[i - num] + arr[i];
+
+    maxSum = Math.max(tempSum, maxSum);
+  }
+
+  return maxSum;
+};
+
+console.log(maxSubarraySum([2, 3], 3));