HDU 2544 最短路重刷,四种算法

题意,赤果果的最短路

想当年傻傻地用floyd和dijkstra乱刷过,最近好好理解了一下最短路,今天用四种算法实现了一遍。

以后可以当模板用。

代码:

floyd

/*
*  Author:      illuz 
*  Blog:        http://blog.csdn.net/hcbbt
*  File:        hdu2544.cpp
*  Create Date: 2013-11-28 15:37:26
*  Descripton:  min path, floyd
*/

#include 
#include 

const int MAXN = 110;
const int INF = 0x3c3c3c3c - 1;

int nn, en;	// num of node and edge
int map[MAXN][MAXN];

int min(int a, int b) {
	return a < b ? a : b;
}

int floyd() {
	for (int k = 1; k <= nn; k++)
		for (int i = 1; i <= nn; i++)
			for (int j = 1; j <= nn; j++)
				map[i][j] = min(map[i][j], map[i][k] + map[k][j]);
}

int main() {
	int s, e, t;
	while (~scanf("%d%d", &nn, &en) && (nn || en)) {
		// init
		for (int i = 1; i <= nn; i++)
			for (int j = 1; j <= nn; j++)
				map[i][j] = INF;
		// input
		for (int i = 0; i < en; i++) {
			scanf("%d%d%d", &s, &e, &t);
			if (t < map[s][e])
				map[s][e] = map[e][s] = t;
		}
		floyd();
		printf("%d\n", map[1][nn]);
	}
	return 0;
}


dijkstra

/*
*  Author:      illuz 
*  Blog:        http://blog.csdn.net/hcbbt
*  File:        hdu2544.cpp
*  Create Date: 2013-11-28 15:37:26
*  Descripton:  min path, dijkstra
*/

#include 
#include 

const int MAXN = 110;
const int INF = 0x3c3c3c3c - 1;

int nn, en;	// num of node and edge
int map[MAXN][MAXN], dis[MAXN];
bool vis[MAXN];

int dijkstra(int s, int e) {
	memset(vis, 0, sizeof(vis));
	// init the dis
	for (int i = 1; i <= nn; i++)
		if (i == s) dis[i] = 0;
		else dis[i] = map[s][i];
	vis[s] = true;
	for (int i = 1; i <= nn; i++) {
		int t = INF, k;
		for (int j = 1; j <= nn; j++)
			if (!vis[j] && t > dis[j])
				t = dis[j], k = j;
		if (t == INF) break;
		vis[k] = true;
		for (int j = 1; j <= nn; j++)
			if (!vis[j] && dis[j] > dis[k] + map[k][j])
				dis[j] = dis[k] + map[k][j];
	}
	return dis[e];
}

int main() {
	int s, e, t;
	while (~scanf("%d%d", &nn, &en) && (nn || en)) {
		// init
		for (int i = 1; i <= nn; i++)
			for (int j = 1; j <= nn; j++)
				map[i][j] = INF;
		// input
		for (int i = 0; i < en; i++) {
			scanf("%d%d%d", &s, &e, &t);
			if (t < map[s][e])
				map[s][e] = map[e][s] = t;
		}
		printf("%d\n", dijkstra(1, nn));
	}
	return 0;
}


bellman ford

/*
*  Author:      illuz 
*  Blog:        http://blog.csdn.net/hcbbt
*  File:        hdu2544.cpp
*  Create Date: 2013-11-28 15:37:26
*  Descripton:  min path, bellman ford 
*/

#include 
#include 
#include 
using namespace std;

const int MAXN = 110;
const int INF = 0x3c3c3c3c - 1;

struct Edge {
	int u, v;
	int cost;
} e[MAXN * MAXN / 2];

int nn, en;	// num of node and edge
int dis[MAXN];

int bellman_ford(int op, int ed) {
	for (int i = 1; i <= nn; i++)
		dis[i] = INF;
	dis[op] = 0;
	for (int i = 0; i < nn - 1; i++)
		for (int j = 0; j < en * 2; j++)
			dis[e[j].v] = min(dis[e[j].v], dis[e[j].u] + e[j].cost);
	return dis[ed];
}

int main() {
	int op, ed, t;
	while (~scanf("%d%d", &nn, &en) && (nn || en)) {
		// input
		for (int i = 0; i < en; i++) {
			scanf("%d%d%d", &op, &ed, &t);
			e[i].u = op; e[i].v = ed; e[i].cost = t;
			e[i + en].u = ed; e[i + en].v = op; e[i + en].cost = t;
		}
		printf("%d\n", bellman_ford(1, nn));
	}
	return 0;
}


spfa+queue

/*
*  Author:      illuz 
*  Blog:        http://blog.csdn.net/hcbbt
*  File:        hdu2544.cpp
*  Create Date: 2013-11-28 15:37:26
*  Descripton:  min path, spfa
*/

#include 
#include 
#include 
#include 
#include 
using namespace std;

const int MAXN = 110;
const int INF = 0x3c3c3c3c - 1;

int nn, en;	// num of node and edge
int map[MAXN][MAXN], dis[MAXN];
bool vis[MAXN]; // if in the queue

int spfa(int op, int ed) {
	queue q;
	memset(vis, false, sizeof(vis));

	for (int i = 1; i <= nn; i++)
		dis[i] = INF;
	dis[op] = 0;

	q.push(op);
	vis[op] = true;

	while (!q.empty()) {
		int cur = q.front();
		q.pop();
		vis[cur] = false;
		for (int i = 1; i <= nn; i++)
			if (dis[i] > dis[cur] + map[cur][i]) {
				dis[i] = dis[cur] + map[cur][i];
				if (!vis[i]) {
					q.push(i);
					vis[i] = true;
				}
			}
	}
	return dis[ed];
}

int main() {
	int op, ed, t;
	while (~scanf("%d%d", &nn, &en) && (nn || en)) {
		// init
		for (int i = 1; i <= nn; i++)
			for (int j = 1; j <= nn; j++)
				map[i][j] = INF;
		// input
		for (int i = 0; i < en; i++) {
			scanf("%d%d%d", &op, &ed, &t);
			if (t < map[op][ed])
				map[op][ed] = map[ed][op] = t;
		}
		printf("%d\n", spfa(1, nn));
	}
	return 0;
}


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