3Sum Closest

    For example, given array S = {-1 2 1 -4}, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

 1 class Solution {
 2 public:
 3     int threeSumClosest( vector<int> &num, int target ) {
 4         int delta = INT_MAX;
 5         sort( num.begin(), num.end() );
 6         for( int i = (int)num.size()-1; i > 1; --i ) {
 7             int s = 0, e = i-1;
 8             while( s < e ) {
 9                 int sum = num[i] + num[s] + num[e];
10                 if( sum == target ) {
11                     return target;
12                 } else if( sum < target ) {
13                     ++s;
14                 } else {
15                     --e;
16                 }
17                 if( abs( sum-target ) < abs( delta ) ) { delta = sum - target; }
18             }
19         }
20         return target + delta;
21     }
22 };