Add Soulution.go for 0016.3Sum Closest

Author: Yeqi Tao

solution/0016.3Sum Closest/Solution.go

@@ -0,0 +1,54 @@
+func threeSumClosest(nums []int, target int) int {
+	sort(nums)
+	lenNums := len(nums)
+	result := nums[0] + nums[1] + nums[2]
+	for i, n := range nums {
+		left := i + 1
+		right := lenNums - 1
+		for left < right {
+			r := nums[left] + nums[right] + n
+			if abs(r - target) < abs(result - target) {
+				result = r
+			}
+			if r > target {
+				right--
+			} else if r < target {
+				left++
+			} else {
+				return result
+			}
+		}
+	}
+	return result
+}
+
+func abs(a int) int {
+	if a >= 0 {
+		return a
+	}
+	return -a;
+}
+
+// quick sort
+func sort(array []int) {
+	if len(array) == 0 {
+		return
+	}
+	left := 0
+	right := len(array) - 1
+	obj := array[left]
+	for left < right {
+		for left < right && array[right] >= obj {
+			right--
+		}
+		array[left] = array[right]
+
+		for left < right && array[left] <= obj {
+			left++
+		}
+		array[right] = array[left]
+	}
+	array[left] = obj
+	sort(array[:left])
+	sort(array[right+1:])
+}