8/21 两数之和

towSum.cpp

+/**
+ * 一次哈希遍历
+ * 解题思路:数值作为map的键，下标作为map的值;
+ * 每次遍历时，如果target-nums[i]在map中能找到值，
+ * 说明target的两个数已经找到,就返回
+*/
+#include <iostream>
+#include<vector>
+#include<map>
+using namespace std;
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        vector<int>res;
+        map<int, int> hashmap;
+        for(int i=0; i< nums.size();i++) {
+            if(hashmap[target-nums[i]] && hashmap[target-nums[i]] != i+1) {
+                res.push_back(i);
+                res.push_back(hashmap[target-nums[i]]-1);
+                return res;
+            }
+
+            //不让hash的下标为负
+            hashmap[nums[i]] = i+1;
+        }
+        return res;
+    }
+};
+int main() {
+    Solution s;
+    vector<int> test= {-2,11, 4, 15, 7,5};
+   
+    for(int i =0; i< s.twoSum(test, 9).size();i++) {
+        cout<< s.twoSum(test, 9)[i]<<endl;
+    }
+    return 0;
+}
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