Merge pull request #613 from openset/develop

Add: 3Sum Closest

Author: Shuo

problems/3sum-closest/3sum_closest.go

@@ -1 +1,31 @@
 package p_3sum_closest
+
+import (
+	"math"
+	"sort"
+)
+
+func threeSumClosest(nums []int, target int) int {
+	sort.Ints(nums)
+	ans, diff, n := math.MaxInt32, math.MaxInt32, len(nums)
+	for i := 0; i < n-2; i++ {
+		l, r := i+1, n-1
+		for l < r {
+			sum := nums[i] + nums[l] + nums[r]
+			if sum < target {
+				if target-sum < diff {
+					ans, diff = sum, target-sum
+				}
+				l++
+			} else if sum > target {
+				if sum-target < diff {
+					ans, diff = sum, sum-target
+				}
+				r--
+			} else {
+				return target
+			}
+		}
+	}
+	return ans
+}

problems/3sum-closest/3sum_closest_test.go

@@ -1 +1,45 @@
 package p_3sum_closest
+
+import "testing"
+
+type caseType struct {
+	input    []int
+	target   int
+	expected int
+}
+
+func TestThreeSumClosest(t *testing.T) {
+	tests := [...]caseType{
+		{
+			input:    []int{-1, 2, 1, -4},
+			target:   1,
+			expected: 2,
+		},
+		{
+			input:    []int{-1, 0, 1, 2, -1, -4},
+			target:   1,
+			expected: 1,
+		},
+		{
+			input:    []int{0, 0, 0, 0},
+			target:   1,
+			expected: 0,
+		},
+		{
+			input:    []int{-2, 0, 0, 2, 2, 2},
+			target:   2,
+			expected: 2,
+		},
+		{
+			input:    []int{-2, 0, 0, 2, 2, 2, 2},
+			target:   1,
+			expected: 0,
+		},
+	}
+	for _, tc := range tests {
+		output := threeSumClosest(tc.input, tc.target)
+		if output != tc.expected {
+			t.Fatalf("input: %v, output: %v, expected: %v", tc.input, output, tc.expected)
+		}
+	}
+}