题解 | 字符串合并处理

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cctype>
#include <sstream>

using namespace std;

string merge(const string s1, const string s2) {
    string ans = s1 + s2;
    int size = ans.size();
    // 按奇偶拆分字符串，分别排序
    string even, odd;
    for (int i = 0; i < size; ++i) {
        i & 1 ? odd.push_back(ans[i]) : even.push_back(ans[i]);
    }
    sort(even.begin(),even.end());
    sort(odd.begin(),odd.end());

    ans.clear();
    for (int i = 0, p = 0, q = 0; i < size; ++i) {
        // 合并时按照原来的奇偶顺序排列
        i & 1 ? ans.push_back(odd[p++]) : ans.push_back(even[q++]);
    }
    return ans;
}

int to_int(char c) {
    if (c >= '0' && c <= '9') return c - '0';
    else if (c >= 'A' && c <= 'F') return c - 'A' + 10;
    else if (c >= 'a' && c <= 'f') return c - 'a' + 10;
    return -1;
}

char reverse_bits(int val) {
    unsigned char m = 0x5;
    unsigned char n = 0x3;
    val = val >> 1 & m | (val & m) << 1;
    val = val >> 2 & n | (val & n) << 2;
    return val < 10 ? val + '0' : val - 10 + 'A'; 
} 

int main() {
    string word1,word2;
    while (cin >> word1 >> word2) {
        string ans;
        for (const auto &c : merge(word1,word2)) {
            int r = to_int(c);
            // 只处理十六进制字符，其他直接添加
            if (r >= 0 && r <= 15)
                ans.push_back(reverse_bits(r));
            else ans.push_back(c);
        }
        cout << ans << endl; 
    }
    return 0;
}