【HDOJ】1104 Remainder

bfs.

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <iostream>
#include <string>
using namespace std;

#define MAXN 1005

char ops[5] = "+-*%";
bool visit[MAXN];
int n, m, k;
string op;

typedef struct node_t {
    int s, n;
    string op;
    node_t (int ss, int nn, string opp) {
        s = ss;
        n = nn;
        op = opp;
    }
} node_t;

int bfs() {
    queue<node_t> Q;
    int ns[4], tmp;
    int nn = ((n+1)%k+k)%k;
    int mk = m*k;

    Q.push(node_t(0, n, ""));
    memset(visit, false, sizeof(visit));
    visit[(n%k+k)%k] = true;

    while(!Q.empty()) {
        node_t nd = Q.front();
        Q.pop();
        // +
        ns[0] = (nd.n + m)%mk;
        // -
        ns[1] = (nd.n - m)%mk;
        // *
        ns[2] = (nd.n * m)%mk;
        // %
        ns[3] = (nd.n % m+m)%m%mk;
        for (int i=0; i<4; ++i) {
            tmp = (ns[i]%k+k)%k;
            if (tmp == nn) {
                op = nd.op + ops[i];
                return nd.s+1;
            }
            if (!visit[tmp]) {
                visit[tmp] = true;
                Q.push(node_t(nd.s+1, ns[i], nd.op+ops[i]));
            }
        }
    }

    return 0;
}

int main() {
    int ans;

#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif

    while (scanf("%d%d%d", &n, &k, &m)!=EOF && (n||m||k)) {
        ans =  bfs();
        printf("%d\n", ans);
        if (ans)
            cout <<op<<endl;
    }

    return 0;
}