leetcode 15 3Sum

Question：Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note:
Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c)
The solution set must not contain duplicate triplets.
For example, given array S = {-1 0 1 2 -1 -4},

A solution set is:
(-1, 0, 1)
(-1, -1, 2)

class Solution {
public:
    vector> threeSum(vector& nums) {
    }

---

这种类型的题目都是一样的，KSum 也只需先排序，然后确定k－2个数，剩下两个数进行夹逼。注意为了跳过重复的三元组所作的努力。

1.夹逼的实现##

    while (j 0)
                {
                    k--;
                    while ( j

2.代码##

//
//  main.cpp
//  leetcode
//
//  Created by YangKi on 15/11/11.
//  Copyright © 2015年 YangKi. All rights reserved.
//

#include
#include
#include
#include
using namespace std;

class Solution {
public:
    vector> threeSum(vector& nums) {
        vector>result;
        int size=nums.size();
        if(size<3) return result;
        sort(nums.begin(), nums.end());
        
        auto last=nums.end();
        
        for ( auto i=nums.begin(); inums.begin() && *i==*(i-1) )//注意：i只需放在每种数的第一个位子，后面的位子不用再放，
                                              //因为在第一个位子得到的种类肯定比放后面的多，而且这样做可以防止得到重复的三元组
            {
                continue;
            }
            
            auto j=i+1;
            auto k=last-1;
            
            while (j 0)
                {
                    k--;
                    while ( j