HDU 1104Remainder

#include<cstdio>
#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
#define MAXN 1000010
int c[MAXN];
int fa[MAXN];
int vis[MAXN];
int s[MAXN];
char op[5] = "+-*%";

int mod(int a, int b) {
    return ( a % b + b) % b;
}

int main() {
    int des, n, k, m, next, now, mo, cnt;
    while (scanf("%d%d%d", &n, &k, &m) != EOF && k) {
        mo = m*k;
        queue <int> q;
        des = mod(n + 1, k);
        n = mod(n, mo);
        memset(vis, 0, sizeof (vis));
        q.push(n);
        vis[n] = 1;
        fa[n] = -1;
        c[n] = -1;
        while (!q.empty()) {
            now = q.front();
            q.pop();
            for (int i = 0; i < 4; ++i) {
                if (i == 0)next = (now + m) % mo;
                else if (i == 1)next = mod(now - m, mo);
                else if (i == 2)next = now * m % mo;
                else next = now % m;
                if (!vis[next]) {
                    vis[next] = 1;
                    fa[next] = now;
                    c[next] = i;
                    if (next % k == des)
                        goto L;
                    q.push(next);
                }
            }
        }
        printf("0
");
        continue;
L:
        cnt = 0;
        while (fa[next] >= 0) {
            s[cnt++] = c[next];
            next = fa[next];
        }
        printf("%d
", cnt);
        while (cnt)
            printf("%c", op[s[--cnt]]);
        printf("
");

    }
    return 0;
}

学会如何输出路径。

还有数论的知识。