POJ 1459 Power Network 最大流

就是給你一個電力網絡，有發電站，有用戶，有中轉站，然後讓你求用戶最多能使用多少電

然後就是網絡流唄，建一個超級源點，連接所有發電站，然後建一個超級匯點，連接所用用戶，然後從超級源點往超級匯點跑網絡流就行

但是因爲是第一次寫，找模板找了好久，最後還是用kuangbin菊苣的模板，畢竟是鏈式前向星的熟悉，而且代碼風格也很熟悉，而且模板也很nice，快的飛起

對了，複雜度應該是O(n*n*sqrt(m))的

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <string>
#include <fstream>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
using namespace std;
//ISAP+bfs 初始化+棧優化
#define maxn 100010//點數的最大值
#define maxm 400010//邊數的最大值
#define INF 0x3f3f3f3f
struct Edge
{
	int to, next, cap, flow;
}edge[maxm];//注意是maxm
int tol;
int head[maxn];
int gap[maxn], dep[maxn], cur[maxn];
void init()
{
	tol = 0;
	memset(head, -1, sizeof(head));
}
void addedge(int u, int v, int w, int rw = 0)
{
	edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0;
	edge[tol].next = head[u]; head[u] = tol++;
	edge[tol].to = u; edge[tol].cap = rw; edge[tol].flow = 0;
	edge[tol].next = head[v]; head[v] = tol++;
}
int Q[maxn];
void BFS(int start, int end)
{
	memset(dep, -1, sizeof(dep));
	memset(gap, 0, sizeof(gap));
	gap[0] = 1;
	int front = 0, rear = 0;
	dep[end] = 0;
	Q[rear++] = end;
	while (front != rear)
	{
		int u = Q[front++];
		for (int i = head[u]; i != -1; i = edge[i].next)
		{
			int v = edge[i].to;
			if (dep[v] != -1)continue;
			Q[rear++] = v;
			dep[v] = dep[u] + 1;
			gap[dep[v]]++;
		}
	}
}
int S[maxn];
int sap(int start, int end, int N)
{
	BFS(start, end);
	memcpy(cur, head, sizeof(head));
	int top = 0;
	int u = start;
	int ans = 0;
	while (dep[start] < N)
	{
		if (u == end)
		{
			int Min = INF;
			int inser;
			for (int i = 0; i < top; i++)
				if (Min > edge[S[i]].cap - edge[S[i]].flow)
				{
					Min = edge[S[i]].cap - edge[S[i]].flow;
					inser = i;
				}
			for (int i = 0; i < top; i++)
			{
				edge[S[i]].flow += Min;
				edge[S[i] ^ 1].flow -= Min;
			}
			ans += Min;
			top = inser;
			u = edge[S[top] ^ 1].to;
			continue;
		}
		bool flag = false;
		int v;
		for (int i = cur[u]; i != -1; i = edge[i].next)
		{
			v = edge[i].to;
			if (edge[i].cap - edge[i].flow && dep[v] + 1 == dep[u])
			{
				flag = true;
				cur[u] = i;
				break;
			}
		}
		if (flag)
		{
			S[top++] = cur[u];
			u = v;
			continue;
		}
		int Min = N;
		for (int i = head[u]; i != -1; i = edge[i].next)
			if (edge[i].cap - edge[i].flow && dep[edge[i].to] < Min)
			{
				Min = dep[edge[i].to];
				cur[u] = i;
			}
		gap[dep[u]]--;
		if (!gap[dep[u]])return ans;
		dep[u] = Min + 1;
		gap[dep[u]]++;
		if (u != start)u = edge[S[--top] ^ 1].to;
	}
	return ans;
}
char s0[20];
int main()
{
	//freopen("input.txt", "r", stdin);
	int n, np, nc, m;
	int u, v, w;
	while (scanf("%d%d%d%d", &n, &np, &nc, &m) != EOF)
	{
		//printf("n %d np %d nc %d m %d\n", n, np, nc, m);
		init();
		n += 2;
		for (int i = 0; i < m; ++i)
		{
			scanf("%s", s0);
			sscanf(s0, "(%d,%d)%d", &u, &v, &w);
			//printf("u %d v %d w %d\n", u, v, w);
			++u; ++v;
			addedge(u, v, w);
		}
		for (int i = 0; i < np; ++i)
		{
			scanf("%s", s0);
			sscanf(s0, "(%d)%d", &v, &w);
			//printf("v %d w %d\n", v, w);
			++v;
			addedge(0, v, w);
		}
		for (int i = 0; i < nc; ++i)
		{
			scanf("%s", s0);
			sscanf(s0, "(%d)%d", &u, &w);
			//printf("u %d w %d\n", u, w);
			++u;
			addedge(u, n - 1, w);
		}
		int ans = sap(0, n - 1, n);
		printf("%d\n", ans);
	}
	//while (1);
	return 0;
}