poj_1459_最大流

题目描述：

   类似1087，基础最大流。化多源多汇点为单源单汇点。

解题思路：

   标准的最大流题目。输入处理用sscanf。数组注意清空。

代码：

#include <stdio.h>
#include <stdlib.h>
#define N 103
#define MAX 1000000

int c[N][N], visit[N], pre[N], n, pn, cn, edge, max_flow, pre[N], visit[N];

void ford_fulkerson(int src, int des){
   int x, y, tmp, min;
   max_flow = 0;
   while(edmonds_karp(src, des)==1){
      min = MAX;
      y = des;
      x = pre[des];
      while(y!=src){
         if(c[x][y] < min)
            min = c[x][y];
         tmp = x;
         x = pre[x];
         y = tmp;
      }  
      max_flow += min;
      y = des;
      x = pre[des];
      while(y!=src){
         c[x][y] -= min;
         c[y][x] += min;
         tmp = x;
         x = pre[x];
         y = tmp;
      }  
   }
}

int edmonds_karp(int src, int des){
   int front, rear, que[10000], v, i;
   memset(visit,0,sizeof(visit));
  
   front = rear = 0;
   que[rear++] = src;
   visit[src] = 1;
   while(front != rear){
      v = que[front++];
      for(i=0;i<=des;i++){
         if(!visit[i] && c[v][i]){
            que[rear++] = i;
            visit[i] = 1;
            pre[i] = v;
           
            if(i == des)
               return 1;
         }
      }
   }
   return 0;
}

main()
{
   int i, j, x, y, z;
   char str[100], *p;
  
   p = (char*)malloc(10*sizeof(char));
  
   while(scanf("%d %d %d",&n, &pn, &cn)!=EOF){
       memset(c,0,sizeof(c));
       scanf("%d",&edge);
       for(i=1;i<=edge;i++){
          scanf("%s",str);
          sscanf(str,"(%d,%d)%d",&x, &y, &z);
          c[x][y] = z;
       }
       for(i=1;i<=pn;i++){
          scanf("%s",str);
          sscanf(str,"(%d)%d",&x, &y);
          c[n][x] = y;
       }
       for(i=1;i<=cn;i++){
          scanf("%s",str);
          sscanf(str,"(%d)%d",&x, &y);
          c[x][n+1] = y;
       }
      
//       for(i=0;i<=n+1;i++){
//          for(j=0;j<=n+1;j++)
//             printf("%d\t",c[i][j]);
//          printf("\n");
//       }

      
       ford_fulkerson(n,n+1);
       printf("%d\n",max_flow);
      
   }
  
   system("pause");
   return 0;
}