First batch of problems

Author: anurag-prakash-singh

3sum-closest.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"sort"
+)
+
+func intAbs(n int) int {
+	return (int)(math.Abs((float64)(n)))
+}
+
+func threeSumClosest(nums []int, target int) int {
+	sort.Ints(nums)
+	result := nums[0] + nums[1] + nums[2]
+
+	for k := 0; k <= len(nums)-3; k++ {
+		i := k + 1
+		j := len(nums) - 1
+
+		if nums[k] > 0 && nums[k] > target {
+			return result
+		}
+
+		for i < j {
+			ijkSum := nums[i] + nums[j] + nums[k]
+
+			if ijkSum == target {
+				return target
+			} else {
+				if intAbs(target-ijkSum) < intAbs(target-result) {
+					result = ijkSum
+				}
+
+				if ijkSum < target {
+					i++
+				} else {
+					j--
+				}
+			}
+		}
+	}
+
+	return result
+}
+
+func main() {
+
+	test1 := []int{-1, 2, 1, -4}
+	ans1 := threeSumClosest(test1, 1)
+
+	fmt.Printf("ans1: %v\n", ans1)
+
+}

3sum.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+func checkIfTriplePresent(result [][]int, triple []int) bool {
+	for _, t := range result {
+		if t[0] > triple[0] {
+			return false
+		}
+
+		if t[0] == triple[0] && t[1] == triple[1] && t[2] == triple[2] {
+			return true
+		}
+	}
+
+	return false
+}
+
+func threeSum(nums []int) [][]int {
+	sort.Ints(nums)
+	result := make([][]int, 0 /*len(nums)*/, 10)
+
+	for k := 0; k <= len(nums)-3; k++ {
+		if k > 0 && nums[k] == nums[k-1] {
+			continue
+		}
+
+		if nums[k] > 0 {
+			break
+		}
+
+		i := k + 1
+		j := len(nums) - 1
+
+		for i < j {
+			ijSum := nums[i] + nums[j]
+
+			if ijSum == -nums[k] {
+				// add to result
+				resultTriple := []int{nums[k], nums[i], nums[j]}
+
+				result = append(result, resultTriple)
+
+				i++
+				j--
+
+				for i < j && nums[i] == nums[i-1] {
+					i++
+				}
+
+				for i < j && nums[j] == nums[j+1] {
+					j--
+				}
+			} else if ijSum < -nums[k] {
+				i++
+			} else {
+				j--
+			}
+		}
+	}
+
+	return result
+}
+
+func main() {
+
+	test1 := []int{-1, 0, 1, 2, -1, -4}
+	ans1 := threeSum(test1)
+
+	fmt.Printf("ans1: %v\n", ans1)
+
+}

4sum.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+// nums is assumed to be pre-sorted
+func threeSum(nums []int, target int) [][]int {
+	result := make([][]int, 0, 10)
+
+	for k := 0; k <= len(nums)-3; k++ {
+		if k > 0 && nums[k] == nums[k-1] {
+			continue
+		}
+
+		i := k + 1
+		j := len(nums) - 1
+
+		for i < j {
+			ijkSum := nums[i] + nums[j] + nums[k]
+
+			if ijkSum == target {
+				// add to result
+				resultTriple := []int{nums[k], nums[i], nums[j]}
+
+				result = append(result, resultTriple)
+
+				i++
+				j--
+
+				for i < j && nums[i] == nums[i-1] {
+					i++
+				}
+
+				for i < j && nums[j] == nums[j+1] {
+					j--
+				}
+			} else if ijkSum < target {
+				i++
+			} else {
+				j--
+			}
+		}
+	}
+
+	return result
+}
+
+func fourSum(nums []int, target int) [][]int {
+	sort.Ints(nums)
+	result := make([][]int, 0, 10)
+
+	for i, v := range nums {
+		if i > 0 && nums[i] == nums[i-1] {
+			continue
+		}
+
+		if i > len(nums)-4 {
+			break
+		}
+
+		fmt.Printf("v: %d; looking for %d in %v\n", v, target-v, nums[i+1:])
+		resultsWOv := threeSum(nums[i+1:], target-v)
+
+		for _, r := range resultsWOv {
+			result = append(result, []int{v, r[0], r[1], r[2]})
+		}
+	}
+
+	return result
+}
+
+func main() {
+
+	test1 := []int{1, -2, -5, -4, -3, 3, 3, 5}
+	ans1 := fourSum(test1, -11)
+	fmt.Printf("ans1: %v\n", ans1)
+
+}

README.md

@@ -0,0 +1 @@
+# leetcode-problems

all-possible-full-binary-trees.go

@@ -0,0 +1,36 @@
+package main
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func allPossibleFBT(N int) []*TreeNode {
+	if N%2 == 0 {
+		return []*TreeNode{}
+	}
+
+	if N == 1 {
+		return []*TreeNode{&(TreeNode{Val: 0, Left: nil, Right: nil})}
+	}
+
+	possibleTrees := make([]*TreeNode, 0, 5)
+
+	for i := 1; i < N-1; i++ {
+		lN := i
+		rN := N - 1 - i
+
+		lTrees := allPossibleFBT(lN)
+		rTrees := allPossibleFBT(rN)
+
+		for _, lTree := range lTrees {
+			for _, rTree := range rTrees {
+				root := TreeNode{Val: 0, Left: lTree, Right: rTree}
+				possibleTrees = append(possibleTrees, &root)
+			}
+		}
+	}
+
+	return possibleTrees
+}

atoi.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func myAtoi(str string) int {
+	sgn := 1
+	num := 0
+	numBegun := false
+	numDigs := 0
+
+	for i := 0; i < len(str); i++ {
+		if numBegun && (str[i] < '0' || str[i] > '9') {
+			break
+		}
+
+		if str[i] == ' ' {
+			continue
+		}
+
+		if str[i] == '-' {
+			sgn = -1
+			numBegun = true
+
+			continue
+		}
+
+		if str[i] == '+' {
+			numBegun = true
+
+			continue
+		}
+
+		if str[i] < '0' || str[i] > '9' {
+			break
+		}
+
+		if num == -1*(1<<31) || num == ((1<<31)-1) {
+			break
+		}
+
+		if str[i] >= '0' && str[i] <= '9' {
+			numBegun = true
+			digit := (int)(str[i] - '0')
+
+			if numDigs == 10 {
+				if sgn == -1 {
+					// Hack ... we don't want -1 being multiplied with INT_MIN (the result will overflow INT_MAX)
+					sgn = 1
+					num = -2147483648
+				} else {
+					num = 2147483647
+				}
+
+				break
+			}
+
+			num = 10*num + digit
+			numDigs = len(fmt.Sprintf("%d", num))
+		}
+	}
+
+	ans := sgn * num
+
+	if ans < math.MinInt32 {
+		return math.MinInt32
+	} else if ans > math.MaxInt32 {
+		return math.MaxInt32
+	} else {
+		return ans
+	}
+}
+
+func main() {
+
+	tests := map[string]int{
+		"1234":           1234,
+		"  1234":         1234,
+		"  ":             0,
+		"  +":            0,
+		"  -":            0,
+		" 1 2":           1,
+		" 1+2":           1,
+		"-1+2":           -1,
+		"++1":            0,
+		"--1":            0,
+		"abcd1234":       0,
+		"  1234 43":      1234,
+		"-91283472332":   -2147483648,
+		"91283472332":    2147483647,
+		" -91283472332 ": -2147483648,
+		" 91283472332 ":  2147483647,
+		"2147483648":     2147483647,
+		"-2147483649":    -2147483648,
+	}
+
+	failures := make(map[string]int)
+	failureMessages := make([]string, 0, len(tests))
+
+	for str, num := range tests {
+		ans := myAtoi(str)
+
+		if ans != num {
+			failureMessages = append(failureMessages, fmt.Sprintf("Test failed for %s. Expected %d, got %d\n", str, num, ans))
+			failures[str] = ans
+		}
+	}
+
+	if len(failures) == 0 {
+		fmt.Printf("All tests passed\n")
+	} else {
+		for _, msg := range failureMessages {
+			fmt.Printf("Failure: %s\n", msg)
+		}
+	}
+
+}