算法面试通关40讲 - 哈希表/映射
1. 两数之和
#include <iostream>
#include <unordered_map>
using namespace std;
class Solution {
public:
vector<int> twoSum(vector<int> &nums, int target) {
vector<int> indices;
unordered_map<int, decltype(nums.size())> left; // val -> index
for (decltype(nums.size()) i = 0; i < nums.size(); ++i) {
auto itr = left.find(target - nums[i]);
if (itr == left.end()) {
left[nums[i]] = i;
} else {
indices.push_back(itr->second);
indices.push_back(i);
break;
}
}
return indices;
}
};