Added 3sum_closest

Author: shichao-an

3sum_closest/solution.py

@@ -0,0 +1,20 @@
+class Solution:
+    # @return an integer
+    def threeSumClosest(self, num, target):
+        num.sort()
+        n = len(num)
+        res = num[0] + num[1] + num[2]
+        for i in range(n - 2):
+            l = i + 1
+            r = n - 1
+            while l < r:
+                s = num[i] + num[l] + num[r]
+                if abs(s - target) < abs(res - target):
+                    res = s
+                if s == target:
+                    return s
+                elif s < target:
+                    l += 1
+                else:
+                    r -= 1
+        return res