uva 10515 - Powers Et Al.(数论)

题目链接：uva 10515 - Powers Et Al.

题目大意：给出m和n，问说mn的个数上的数是多少。

解题思路：其实只要看m的最后一位数就可以了，判断最有一位的周期，然后用n%t即可。

#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;

const int maxn = 15;
const int maxs = 105;

vector<int> g[maxn];
char a[maxs], b[maxs];

void init () {

    int v[maxn];
    for (int i = 0; i < maxn; i++) {

        int tmp = i;
        memset(v, 0, sizeof (v));

        while (v[tmp] == 0) {
            v[tmp] = 1;
            g[i].push_back(tmp);
            tmp = tmp * i % 10;
        }
    }
}

int main () {
    init();
    while (scanf("%s%s", a, b) == 2 && ( strcmp(a,"0") || strcmp(b,"0")) ) {

        if (strcmp(b, "0") == 0) {
            printf("1\n");
            continue;
        }

        int u = a[strlen(a)-1] - ‘0‘;
        int len = strlen(b);

        int tmp = 1, m = g[u].size();
        for (int i = 0; i < len; i++)
            tmp = (tmp * 10 + (b[i] - ‘0‘)) % m;
        printf("%d\n", g[u][(tmp-1+m)%m]);
    }
    return 0;
}

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