poj 1135 Domino Effect

留下代码

有空写解题报告 蛋疼的题目

#include<stdio.h>
const int MAXN = 501;
const int INF = 0x3f3f3f3f;
int n, m;
int map[MAXN][MAXN], dist[MAXN];
bool used[MAXN];
void dijkstra(){
    for(int i = 1; i <= n; ++i){
        dist[i] = map[1][i];
        used[i] = false;
    }
    used[1] = true;
    dist[1] = 0;
    for(int i = 1; i < n; ++i){
        int min = INF, minidx;
        for(int j = 1; j <= n; ++j){
            if(!used[j] && min > dist[j])
                min = dist[minidx = j];    //这种写法不错 简洁 也易懂 
        }
        used[minidx] = true;
        for(int j = 1; j <= n; ++j){
            if(!used[j] && dist[j] > dist[minidx] + map[minidx][j])
                dist[j] = dist[minidx] + map[minidx][j];
        }
    }
}
int main(){
    int a, b, c ,cases = 1;;
    while(scanf("%d%d",&n, &m) == 2, n){
        for(int i = 1; i <= n; ++i){
            for(int j = 1; j <= n; ++j){
                map[i][j] = INF;
            }
            map[i][i] = 0;
        }
        for(int i = 0; i < m; ++i){
            scanf("%d%d%d",&a, &b, &c);
            map[a][b] = map[b][a] = c;
         }
        dijkstra();
        int max = dist[1], key = 1, aa, bb;//k置为1 对付n=1，m=0 这组数据
        bool flag = true;
        for(int i = 2; i <= n; ++i)
            if(max < dist[i])
                max = dist[key = i];
        max *= 2;
        for(int i = 1; i <= n; ++i){
            for(int j = 1; j <= n; ++j){
                if( map[i][j] != INF && dist[j] < map[i][j] + dist[i]){
                    if(dist[i] + dist[j] + map[i][j] > max){
                        max = dist[aa = i] + dist[bb = j] + map[i][j];
                        flag = false;
                        if(a > b)
                             a ^= b ^= a ^= b;
                    }
                }
            }
        }
        printf("System #%d\n",cases++);
        if(flag)
            printf("The last domino falls after %d.0 seconds, at key domino %d.\n",max / 2, key);
        else
            printf("The last domino falls after %.1lf seconds, between key dominoes %d and %d.\n",(double)max / 2, aa , bb );
        printf("\n");
    }    
    return 0;
}