HDU - 1596 find the safest road （最短路水题）

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题目大意：找出两点见安全系数最高的那条路

解题思路：直接最短路解决

#include <cstdio>#include <cstring>#include <cmath>#include <queue>#define INF 0x3f3f3f3f#define N 1010#define M 1000010#define esp 1e-8using namespace std;struct Node {    int to, next;    double len;}node[M];int n, m, cnt, s, e, head[N];bool vis[N];double d[N], dis[N][N];void init() {    double x;    for (int i = 1; i <= n; i++)        for (int j = 1; j <= n; j++) {            scanf("%lf", &dis[i][j]);        }}bool dij() {    bool flag = false;;    for (int i = 1; i <= n; i++) {        d[i] = 0.0;        vis[i] = false;    }    d[s] = 1.0;    for (int i = 1; i <= n - 1; i++) {        int x;        double tmp = 0.0;        for (int j = 1; j <= n; j++) {            if (!vis[j] && d[j] - tmp > esp) {                tmp = d[j];                x = j;            }        }        if (x == e)            return true;        vis[x] = true;        for (int j = 1; j <= n; j++) {            if (!vis[j] && d[x] * dis[x][j] - d[j] > esp) {                d[j] = d[x] * dis[x][j];                if (j == e)                    flag = true;            }        }    }    return flag;} void solve() {    scanf("%d", &m);    int x, y;    for (int i = 0; i < m; i++) {        scanf("%d%d", &s, &e);        if (!dij())            printf("What a pity!\n");        else            printf("%.3lf\n", d[e]);    }}int main() {    while (scanf("%d", &n) != EOF) {        init();        solve();    }    return 0;}

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