network flow based on BFS

Hello,everyone.Long time no meeting.Graph theory is a little difficult for me.Because the code is difficult to write.And i have not learned STL yet.So i spend so time to find my own data structure,and spend a lot of time to get my code passed.Luckily,i
find my ability is growing day by day.Now i can easily find the mistakes in my code.

Have fun coding,i_human.Have fun coding,everyone!

// 网络流算法 BFS.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include<iostream>
#define a 100
#define m 1000

using namespace std;

int n,e,s,t,l;
int f=0;
int flow[a][a],pre[2][a],rec[a][a],cap[a][a],relpre[a];

bool find();
void operate();

int main()
{
int u,v,w;
cin>>s>>t;
for(int i=0;i<a;i++)
for(int j=0;j<a;j++)
{
flow[i][j]=0;
cap[i][j]=0;
rec[i][j]=0;
}
for(int i=0;i<a;i++)
{
pre[0][i]=0;
pre[1][i]=0;
relpre[i]=0;
}
pre[0][0]=s;
pre[1][0]=0;
relpre[s]=s;
cin>>n>>e;
for(int i=0;i<e;i++)
{
cin>>u>>v>>w;
cap[u][v]=w;
rec[u][0]++;
rec[u][rec[u][0]]=v;
}
for(int i=1;i<=n;i++)
{
for(int j=0;j<=n;j++)
cout<<rec[i][j]<<" ";
cout<<endl;
}
while(find())
{
operate();
for(int i=1;i<=n;i++)
relpre[i]=0;
relpre[s]=s;
pre[0][0]=s;
pre[1][0]=0;
}
cout<<f<<endl;
system("pause");
return 0;
}

bool find()
{
int start=pre[1][0];
int end=pre[1][0];
bool flag=0;
int num=0;
l=pre[1][0]+1;
while(flag==0 && l<=n)
{
num=0;
for(int i=start;i<=end;i++)
{
for(int j=1;j<=rec[pre[0][i]][0];j++)
{
if(relpre[rec[pre[0][i]][j]]!=0)
continue;
if(relpre[rec[pre[0][i]][j]]==0)
{
pre[0][end+j]=rec[pre[0][i]][j];
pre[1][end+j]=l;
relpre[rec[pre[0][i]][j]]=pre[0][i];
num++;
}
if(rec[pre[0][i]][j]==t)
{
flag=1;
return flag;
}
}
}
l++;
start=end+1;
end=end+num;
}
return flag;
}

void operate()
{
int path[a];
int min=a;
int r=t;
int pot;
path[l]=t;
for(int i=l-1;i>=0;i--)
{
path[i]=relpre[r];
r=relpre[r];
}
for(int i=0;i<l;i++)
{
if(cap[path[i]][path[i+1]]<min)
min=cap[path[i]][path[i+1]];
}
f+=min;
for(int i=0;i<l;i++)
{
cap[path[i]][path[i+1]]-=min;
flow[path[i]][path[i+1]]+=min;
if(cap[path[i]][path[i+1]]==0)
{
for(int j=1;j<=rec[path[i]][0];j++)
{
if(rec[path[i]][j]==path[i+1])
{
pot=j;
break;
}
}
if(pot!=rec[path[i]][0])
{
for(int k=pot+1;k<=rec[path[i]][0];k++)
rec[path[i]][k-1]=rec[path[i]][k];
}
rec[path[i]][0]--;
}
}
}