poj 2917（高斯消元。。。。。泪水呀）

做了一天多了吧。。。。先是学习大牛们的优化版的程序。。。。不知道哪里写错了。。。就是不过。。。最后还是自己按线性代数的解方程一步步来的。。。。AC是AC了。。效率不是很高的。。。。。。今天网络赛就耽误了一下。。。现在终于写好了。。。泪水呀。。。。

好像是discuss里提到多解的时候如果不是仔细判断的也有可能是无解的情况。。。。这个貌似要注意。。不过我这样直接解的就飘过了。。。。

#include<iostream>
#include<cstdio>
#include<string>
#include<map>
using namespace std;
map<string, int> q;
int a[310][310], ans[310], n, m;

inline void init1() {
    q["MON"] = 0, q["TUE"] = 1, q["WED"] = 2, q["THU"] = 3;
    q["FRI"] = 4, q["SAT"] = 5, q["SUN"] = 6;
}

int ex_gcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1, y = 0;
        return a;
    }
    int d = ex_gcd(b, a % b, x, y), t = x;
    x = y, y = t - a / b*y;
    return d;
}

int gauss() {
    int i, j, k, t, x, y;
    for (i = 1, j = 1; i <= m && j <= n; i++, j++) {
        k = i;
        while (k <= m && a[k][j] == 0)
            k++;
        if (k == m + 1) {
            i--;
            continue;
        }
        if (k != i)
            for (t = 1; t <= n + 1; t++)
                swap(a[k][t], a[i][t]);
        for (k = 1; k <= m; k++)
            if (k != i && a[k][j] != 0) {
                x = a[i][j], y = a[k][j];
                for (t = 1; t <= n + 1; t++) {
                    a[k][t] = a[k][t] * x - a[i][t] * y;
                    a[k][t] = (a[k][t] % 7 + 7) % 7;
                }
            }
    }
    int d, sum = 0;
    for (i = 1; i <= m; i++) {
        for (j = i; j <= n && a[i][j] == 0; j++);
        if (j >= n + 1) {
            if (a[i][n + 1] == 0) sum++;
            else return -1;
        } else {
            d = ex_gcd(a[i][j], 7, x, y);
            if (a[i][n + 1] % d != 0) return -1;
            ans[j] = (x * (a[i][n + 1] / d) % 7 + 7) % 7;
            while (ans[j] < 3) ans[j] += 7;
            while (ans[j] > 9) ans[j] -= 7;
        }
    }
    if (m - sum < n) return 1;
    return 0;
}

int main() {
    int i, ret, k, s;
    string str1, str2;
    init1();
    while (scanf("%d%d", &n, &m) && (n || m)) {
        memset(a, 0, sizeof (a));
        for (i = 1; i <= m; i++) {
            cin >> s >> str1 >> str2;
            a[i][n + 1] = (q[str2] - q[str1] + 8) % 7;
            while (s--) {
                scanf("%d", &k);
                a[i][k] += 1, a[i][k] %= 7;
            }
        }
        ret = gauss();
        if (ret == -1)
            printf("Inconsistent data.\n");
        else if (ret == 1)
            printf("Multiple solutions.\n");
        else {
            for (i = 1; i < n; i++)
                printf("%d ", ans[i]);
            printf("%d\n", ans[n]);
        }
    }
    return 0;
}