sap模板

SpringWater(GHQ)总结：

#include <stdio.h>  
#include <string.h>  
#define MAXN 100010  
#define MAXE 400010  
const int INF = 0x3f3f3f3f;  
struct Edge  
{  
    int to, from, next, cap;  
}edge[MAXE];  
  
int head[MAXN],cnt,n,m,src,des;  
int dep[MAXN], gap[MAXN];  
  
void addedge(int cu, int cv, int cw)  
{  
    edge[cnt].from = cu;  
    edge[cnt].to = cv;  
    edge[cnt].cap = cw;  
    edge[cnt].next = head[cu];  
    head[cu] = cnt++;  
    edge[cnt].from = cv;  
    edge[cnt].to = cu;  
    edge[cnt].cap = 0;  
    edge[cnt].next = head[cv];  
    head[cv] = cnt++;  
}  
  
int que[MAXN];  
  
void BFS()  
{  
    memset(dep, -1, sizeof(dep));  
    memset(gap, 0, sizeof(gap));  
    gap[0] = 1;  
    int front = 0, rear = 0;  
    dep[des] = 0;  
    que[rear++] = des;  
    int u, v;  
    while (front != rear)  
    {  
        u = que[front++];  
        front = front%MAXN;  
        for (int i=head[u]; i!=-1; i=edge[i].next)  
        {  
            v = edge[i].to;  
            if (edge[i ^1].cap == 0 || dep[v] != -1)  
                continue;  
            que[rear++] = v;  
            rear = rear % MAXN;  
            ++gap[dep[v] = dep[u] + 1];  
        }  
    }  
}  
int cur[MAXN],stack[MAXN];  
int Sap()       //sap模板  
{  
    int res = 0;  
    BFS();  
    int top = 0;  
    memcpy(cur, head, sizeof(head));  
    int u = src, i;  
    while (dep[src] < n)  
    {  
        if (u == des)  
        {  
            int temp = INF, inser = n;  
            for (i=0; i!=top; ++i){  
                if (temp > edge[stack[i]].cap){  
                    temp = edge[stack[i]].cap;  
                    inser = i;  
                }  
            }  
            for (i=0; i!=top; ++i)  
            {  
                edge[stack[i]].cap -= temp;  
                edge[stack[i]^1].cap += temp;  
            }  
            res += temp;  
            top = inser;  
            u = edge[stack[top]].from;  
        }  
  
        if (u != des && gap[dep[u] -1] == 0)  
            break;  
        for (i = cur[u]; i != -1; i = edge[i].next)  
            if (edge[i].cap != 0 && dep[u] == dep[edge[i].to] + 1)  
                break;  
  
        if (i != -1)  
        {  
            cur[u] = i;  
            stack[top++] = i;  
            u = edge[i].to;  
        }  
        else  
        {  
            int min = n;  
            for (i = head[u]; i != -1; i = edge[i].next)  
            {  
                if (edge[i].cap == 0)  
                    continue;  
                if (min > dep[edge[i].to])  
                {  
                    min = dep[edge[i].to];  
                    cur[u] = i;  
                }  
            }  
            --gap[dep[u]];  
            ++gap[dep[u] = min + 1];  
            if (u != src)  
                u = edge[stack[--top]].from;  
        }  
    }  
    return res;  
}  
int main()  
{  
    int T, i;  
    int cas = 0;
    freopen("in.txt", "r", stdin);
    scanf("%d", &T);  
    while (T--)  
    {  
        scanf("%d%d", &n, &m);  
    src = 0;//源点为0
    des = n - 1;//汇点为n-1
        cnt = 0;  
        memset(head, -1, sizeof(head));  
        int u, v, c;  
    printf("Case: %d\n", ++cas);
        for (i  =0; i < m; ++i)  
        {  
            scanf("%d%d%d", &u, &v, &c);  
        --u, --v;//输入是从1点开始，而src是从0点开始
            addedge(u,v,c);  
            addedge(v,u,c);  //流量为双向，如果是单向得去掉这句
        int ans = Sap();  
        if(ans)   printf("%d\n", ans);  
        }  

    }  
    return 0;  
}