HDU 1874 畅通工程续 + HDU 2544 最短路 最短路水题，floyd水

题目：

1874 http://acm.hdu.edu.cn/showproblem.php?pid=1874

2444 http://acm.hdu.edu.cn/showproblem.php?pid=2544

裸单源最短路径。。。水题。。。

用很水的方法，floyd水果，复杂度n^3很吓人啊。。。。慢慢学各种最短路算法，这几题都要再用各种方法水一遍。。。

最近考试，伤不起呢。。。

1874：

#include <cstdio>
#include <cstring>
using namespace std;
#define INF 10000
const int maxn = 201;
int r[maxn][maxn];

int main() {
    int n, m;
    while (scanf("%d%d", &n, &m) != EOF) {
        memset (r, INF, sizeof(r));
        int x, y, v;
        for (int i = 0; i < m; i++) {
            scanf("%d%d%d", &x, &y, &v);
            if (r[x][y] > v)
                r[x][y] = r[y][x] = v;
        }//for
        for (int i = 0; i < n ;i++)
            r[i][i] = 0;
        for (int k = 0; k < n; k++)
            for (int i = 0; i < n; i++)
                for (int j = 0; j < n; j++) {
                    if (r[i][k] + r[k][j] < r[i][j])
                        r[i][j] = r[j][i] = r[i][k] + r[k][j];
                }//for
        scanf("%d%d", &x, &y);
        if (r[x][y] < INF)
            printf("%d\n", r[x][y]);
        else
            printf("-1\n");
    }//while
    return 0;
}//hehe

2444

#include <cstdio>
#include <cstring>
#define INF 0xfffff
const int maxn = 1002;
int p[maxn][maxn];

int main() {
    int n, m;
    int i, j, k;
//    freopen("in", "r", stdin);
    while (scanf("%d%d", &n, &m) && n && m) {
        for (i = 1; i <= n; i++)
            for (j = 1; j <= n; j++)
                if (j == i)
                    p[i][j] = p[j][i] = 0;
                else
                    p[i][j] = p[j][i] = INF;
        int x, y, w;
        for (i = 0; i < m; i++) {
            scanf("%d%d%d", &x, &y, &w);
            if (p[x][y] > w)
                p[x][y] = p[y][x] = w;
        }
        for (i = 1; i <= n; i++)
            for (j = 1; j <= n; j++)
                for (k = 1; k <= n; k++)
                    if (p[i][k] + p[k][j] < p[i][j])
                        p[i][j] = p[j][i] = p[i][k] + p[k][j];
        printf("%d\n", p[1][n]);
    }
}