【HDOJ】3419 The Three Groups

记忆化搜索。

/* 3419 */
#include <cstdio>
#include <cstring>
#include <cstdlib>

#define MAXN 10

int ans;
int n[3];
int x[3];
bool visit[MAXN];
int cnt[MAXN][MAXN][MAXN];

void dfs(int d, int i, int v) {
    if (i == 3) {
        if (x[0]*x[1] == x[2])
            ++ans;
        return ;
    }
    if (d < n[i]) {
        for (int j=1; j<MAXN; ++j) {
            if (!visit[j]) {
                visit[j] = true;
                dfs(d+1, i, v*10+j);
                visit[j] = false;
            }
        }
    } else {
        x[i] = v;
        dfs(0, i+1, 0);
    }
}

int main() {
    int a, b, c;
    int i, j, k;
    
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    memset(cnt, -1, sizeof(cnt));
    while (scanf("%d %d %d", &a, &b, &c)!=EOF && (a||b||c)) {
        if (a+b < c) {
            puts("0");
        } else if (a>c || b>c){
            puts("0");
        } else if (a+b-c>1) {
            puts("0");
        } else if (cnt[a][b][c] >= 0) {
            printf("%d
", cnt[a][b][c]);
        } else {
            memset(visit, false, sizeof(visit));
            n[0] = a;
            n[1] = b;
            n[2] = c;
            ans = 0;
            dfs(0, 0, 0);
            cnt[a][b][c] = ans;
            printf("%d
", ans);
        }
    }
    
    return 0;
}