Referência para Leonardo's Notebook (LA 3641)

#include <stdio.h>
#include <algorithm>
#include <string.h>
using namespace std;

int perm[30];
int cycle[30];
int _42;
bool mark[30];

int main() {
    scanf("%d", &_42);

    while (_42--) {
        char tmp[30];
        scanf(" %s", tmp);

        memset(mark,false,sizeof(mark));
        memset(cycle,0,sizeof(cycle));

        for (int i=0; i<26; i++)
            perm[i]=tmp[i]-'A';

        for (int i=0; i<26; i++)
            if (!mark[i]) {
                int cnt=0, pos=i;

                while (!mark[pos]) {
                    mark[pos]=true, cnt++;
                    pos=perm[pos];
                }
                cycle[cnt]++;
            }

        bool can=true;
        for (int i=1; i<=26; i++)
            if (i%2==0 && cycle[i]%2)
                can=false;

        printf("%s\n", can? "Yes":"No");
    }

    return 0;
}