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