HDU3853（期望）

题目很水了，但是原地打转的点……虽然不难想到这个坑，但是从数学的角度来讲期望不应该算正无穷嘛……为什么算0啊？

 

const int maxn = 1e3 + 5;
const db eps = 1e-5;
int R, C;
struct gird {
    db ori, right, down;
}p[maxn][maxn];
db E[maxn][maxn];

int main() {
    while (scanf("%d %d", &R, &C) != EOF) {
        rep(i, 1, R) {
            rep(j, 1, C) {
                scanf("%lf %lf %lf", &p[i][j].ori, &p[i][j].right, &p[i][j].down);
                E[i][j] = 0;
            }
        }
        irep(i, R, 1) {
            irep(j, C, 1) {
                if (i == R && j == C)    continue;
                if (fabs(1 - p[i][j].ori) < eps)    continue;
                if (i < R)    E[i][j] += E[i + 1][j] * p[i][j].down;
                if (j < C)    E[i][j] += E[i][j + 1] * p[i][j].right;
                E[i][j] += 2;
                E[i][j] /= (1 - p[i][j].ori);
            }
        }
        printf("%.3lf\n", E[1][1]);
    }
    return 0;
}