不知道这么写行不行 #include <stdio.h>  #include <iostream>  #include <vector>  #include <deque>  #include <queue>  #include <set>  #include <stack>  #include <map>  #include<algorithm> #include<string> #include<functional> using namespace std; int main() { char s1[100];  while (gets(s1)){ int len = strlen(s1); int end = 99; for (int i = len - 1; i >= 0; i--){ if (s1[i] == 'C') { s1[end--] = 'D'; s1[end--] = 'C'; s1[i] = '#'; } else if ((i > 0) && (s1[i] == 'B'&&s1[i - 1] == 'A')){ s1[end--] = 'B'; s1[i] = '#'; i--; s1[i] = '#'; } else{ s1[end--] = s1[i]; s1[i] = '#'; } } for (int i = 0; i < 100; i++){ if (s1[i] >= 'A'&&s1[i] <= 'Z') cout << s1[i]; } } return 0; }