Three sum closest

Signed-off-by: Leo Ma <[email protected]>

016_three_sum_closest/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test three_sum_closest.c -lm

016_three_sum_closest/three_sum_closest.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <limits.h>
+
+static void insert_sort(int *a, int size)
+{
+    int i, j;
+    for (i = 1; i < size; i++) {
+        int tmp = a[i];
+        for (j = i - 1; j >= 0 && a[j] > tmp; j--) {
+            a[j + 1] = a[j];
+        }
+        a[j + 1] = tmp;
+    }
+}
+
+static int threeSumClosest(int* nums, int numsSize, int target) {
+    int i, min_diff = INT_MAX;
+
+    if (numsSize < 3) {
+        return min_diff;
+    }
+
+    insert_sort(nums, numsSize);
+
+    for (i = 0; i < numsSize - 2; i++) {
+        int left = i + 1;
+        int right = numsSize - 1;
+        while (left < right) {
+            int diff = nums[i] + nums[left] + nums[right] - target;
+            if (abs(diff) < abs(min_diff)) {
+                min_diff = diff;
+            }
+            if (diff < 0) {
+                left++;
+            } else if (diff > 0) {
+                right--;
+            } else {
+                break;
+            }
+        }
+    }
+    return min_diff + target;
+}
+
+int main(void)
+{
+    int i, target = 1;
+    int nums[] = { -1, 2, 1, -4 };
+    printf("%d\n", threeSumClosest(nums, sizeof(nums) / sizeof(nums[0]), target));
+    return 0;
+}