数对和
- 难度:Medium
- 题目链接:https://leetcode-cn.com/problems/pairs-with-sum-lcci/
题目描述
设计一个算法,找出数组中两数之和为指定值的所有整数对。一个数只能属于一个数对。
示例 1:
输入: nums = [5,6,5], target = 11 输出: [[5,6]]
示例 2:
输入: nums = [5,6,5,6], target = 11 输出: [[5,6],[5,6]]
提示:
nums.length <= 100000
解法:
和 twosum 类似的思路。
class Solution {
public:
vector<vector<int>> pairSums(vector<int>& nums, int target) {
vector<vector<int>> ret;
unordered_map<int, int> num_to_count;
for(int num: nums){
int other = target - num;
if(num_to_count.find(other) != num_to_count.end() && num_to_count[other] > 0){
ret.emplace_back(vector<int>({num, target-num}));
num_to_count[other]--;
}else{
num_to_count[num]++;
}
}
return ret;
}
};