129 - Krypton Factor （UVA）

题目链接如下：

Online Judge

代码如下：

#include <cstdio>
// #define debug

int n, L, cnt;
char letters[] = " ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char ans[80];

bool isHard(int k){
    for (int i = k - 1; i >= 0; --i){
        if (ans[i] != ans[k] || i + 1 < k - i){
            continue;
        }
        int flag = 1;
        for (int j = i + 1; j < k; ++j){
            if (ans[j] != ans[j - (k - i)]){
                flag = 0;
                break;
            }
        }
        if (flag){
            return false;
        }
    }
    return true;
}

void generate(int k){
    if (cnt >= n){
        return;
    }
    if (k != 0){
        ++cnt;
    }
    if (cnt == n){
        for (int i = 0; i < k; ++i){
            printf("%c", ans[i]);
            if (i == 63){
                printf("%s", i == k - 1 ? "" : "\n");
            } else if (i != k - 1 && i % 4 == 3){
                printf(" ");
            }
        }
        printf("\n%d\n", k);
        return;
    }
    for (int i = 1; i <= L; ++i){
        ans[k] = letters[i];
        if (isHard(k)){
            generate(k + 1);
        }
    }
}

int main(){
    #ifdef debug
    freopen("0.txt", "r", stdin);
    freopen("1.txt", "w", stdout);
    #endif
    while (scanf("%d %d", &n, &L) == 2 && (n || L)){
        cnt = 0;
        generate(0);
    }
    #ifdef debug
    fclose(stdin);
    fclose(stdout);
    #endif
    return 0;
}