【leetcode】3Sum Closest

3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    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).

 

与 3Sum类似，只是需要添加一个变量distance，用来记录和target距离最小的a+b+c

 

 class Solution {
 public:
     int threeSumClosest(vector<int> &num, int target) {

         int n=num.size();
         sort(num.begin(),num.end());

         int i,j,k;
         int a,b,c;
         int result;
         int distance=INT_MAX;

         for(i=;i<n-;i++)
         {
             j=i+;
             k=n-;

             while(j<k)
             {
                 a=num[i];
                 if(i>&&num[i]==num[i-])
                 {
                     break;
                 }
                 b=num[j];
                 if(j>i+&&num[j]==num[j-])
                 {
                     j++;
                     continue;
                 }

                 c=num[k];
                 if(k<n-&&num[k]==num[k+])
                 {
                     k--;
                     continue;
                 }

                 if(a+b+c==target)
                 {
                     return target;
                 }
                 else if(a+b+c<target)
                 {
                     if(target-(a+b+c)<distance)
                     {
                         result=a+b+c;
                         distance=target-result;
                     }
                     j++;
                 }
                 else if(a+b+c>target)
                 {
                     if((a+b+c)-target<distance)
                     {
                         result=a+b+c;
                         distance=result-target;
                     }
                     k--;
                 }
             }
         }

         return result;

     }
 };