hdu2962 Trucking

来源：互联网发布：双色球关注倾向数据编辑：程序博客网时间：2024/06/05 07:20
算是简单题目，遇到有两个变量同时变化时，一般的做法是二分一个变量，求另外一个变量。
#include <iostream>#include <cstdio>#include <cstring>using namespace std;const int M = 1005;const int inf = 9999999;int dist[M][M];int hight[M][M];int s, e, maxn, minn, len;int n, m, ans, Case= 1, mid;void init() {    minn = inf;    ans = -1;    len = inf;    for(int i = 1; i <= n; i++) {        for(int j = 1; j <= n; j++){            dist[i][j] = inf;            hight[i][j] = 0;        }    }}void input() {    int x, y, h, d;     for(int i = 0; i < m; i++) {            scanf("%d%d%d%d", &x, &y, &h, &d);                dist[x][y] = dist[y][x] = d;            if(h == -1){                hight[x][y] = hight[y][x] = inf;            }else {                    hight[x][y] = hight[y][x] = h;            }            if(h != -1)            minn = min(h, minn);        }    scanf("%d%d%d", &s,&e, &maxn);    if(Case > 1)            printf("\n");}int Dijstra(int mid) {    int dis[M];    int vist[M];    int index, mmin;    for(int i = 1; i <= n; i++) {       if(hight[s][i] >= mid){            dis[i] = dist[s][i];        }else {           dis[i] = inf;       }        vist[i] = 0;    }    dis[s] = 0;    vist[s] = 1;    for(int k = 0; k <= n; k++) {        mmin = inf;        for(int i = 1; i <= n; i++) {            if(!vist[i] &&dis[i] < mmin) {                mmin = dis[i];                index = i;            }        }        if(mmin == inf)            break;        vist[index] = 1;        for(int i = 1; i <= n; i++) {            if(!vist[i] && dis[i] > dis[index] + dist[index][i] && hight[index][i] >= mid) {                dis[i] = dis[index] + dist[index][i];            }        }    }   return dis[e];}void work() {    int temp;     mid = (maxn + minn)/2;    while(maxn >= minn) {        temp = Dijstra(mid);        if(temp != inf){            ans = mid;            len = temp;            minn = mid + 1;        }else {            maxn = mid - 1;        }         mid = (maxn + minn)/2;    }}void output() {     printf("Case %d:\n", Case++);    if(ans != -1) {   printf("maximum height = %d\n", ans);   printf("length of shortest route = %d\n", len);    }else {        printf("cannot reach destination\n");    }}int main(){    while(scanf("%d%d", &n, &m) != EOF && (n || m)) {        init();        input();        work();        output();    }    return 0;}
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