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).
算法：固定第一个，另外两个数适用双指针。O(N^2)
java：
public class Solution {
public int threeSumClosest(int[] num, int target) {
int len=num.length;
int distance=Integer.MAX_VALUE;
int sum=0;
Arrays.sort(num);
for(int i=0;i<len-2;i++){
int s=i+1;
int e=len-1;
while(s<e){
int cnt= num[i]+num[s]+num[e];
int dis = Math.abs(target-cnt);
if(dis<=distance){
sum=cnt;
distance=dis;
if(sum==target){
return sum;
}else if(sum<target){
s++;
}else {
e--;
}
}else if(cnt<target){
s++;
}else{
e--;
}
}
}
return sum;
}
}
c++:
class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
int size=num.size();
sort(num.begin(),num.end());
int close=0;
int dis=INT_MAX;
for(int i=0;i<size-2;i++){
int j=i+1;
int k=size-1;
while(j<k){
int sum=num[i]+num[j]+num[k];
if(abs(sum-target)<=dis){
dis=abs(sum-target);
close=sum;
if(sum==target){
return close;
}else if(sum<target){
j++;
}else{
k--;
}
}else if(sum-target<0){
j++;
}else{
k--;
}
}
}
return close;
}
};