将map<string> map1和map<string> map2合并为map<string,string> map3

可以使用迭代器遍历map1和map2，将它们的键值对存入map3中。代码示例如下：

#include <iostream>
#include <map>
#include <string>

using namespace std;

int main() {
    map<string, string> map3;
    map<string, string> map1 = {{"key1", "value1"}, {"key2", "value2"}};
    map<string, string> map2 = {{"key3", "value3"}, {"key4", "value4"}};

    // 将map1中的键值对存入map3中
    for (auto it = map1.begin(); it != map1.end(); ++it) {
        map3[it->first] = it->second;
    }

    // 将map2中的键值对存入map3中
    for (auto it = map2.begin(); it != map2.end(); ++it) {
        map3[it->first] = it->second;
    }

    // 遍历输出map3中的键值对
    for (auto it = map3.begin(); it != map3.end(); ++it) {
        cout << it->first << ": " << it->second << endl;
    }

    return 0;
}

输出结果为：

key1: value1
key2: value2
key3: value3
key4: value4