（重刷）HDU 1874 畅通工程续 + HDU 2544 最短路最短路水题，dijkstra解法。

最新推荐文章于 2021-05-28 20:01:21 发布

iteye_4389

最新推荐文章于 2021-05-28 20:01:21 发布

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本文通过两个HDU在线评测系统的题目，介绍了Dijkstra算法的具体实现过程。包括如何初始化距离数组、路径数组，以及如何选取最短路径节点进行松弛操作等关键步骤。

floyd解法

今天初看dijkstra，先拿这两题练手，其他变形题还是不是很懂。

模版题，纯练打字。。。

HDU 1874：

#include <cstdio>

#define MAXN 200
#define INF 0xfffff 

int n;
int Edge[MAXN][MAXN];
int s[MAXN];
int dist[MAXN];
int path[MAXN];

void Dijkstra(int v0) {
	int i, j, k;
	for (i = 0; i < n; i++) {
		dist[i] = Edge[v0][i];
		s[i] = 0;
		if (i != v0 && INF > dist[i])
			path[i] = v0;
		else
			path[i] = -1;
	}
	s[v0] = 1;
	dist[v0] = 0;
	for (i = 0; i < n - 1; i++) {
		int min = INF, u = v0;
		for (j = 0; j < n; j++)
			if (!s[j] && dist[j] < min){
				u = j;
				min = dist[j];
			}//if
		s[u] = 1;
		for (k = 0; k < n; k++) {
			if (!s[k] && Edge[u][k] < INF && dist[u] + Edge[u] [k] < dist[k]) {
				dist[k] = dist[u] + Edge[u][k];
				path[k] = u;
			}//if
		}//for
	}//for
}

int main() {
	int m;
	int i, j;
	while (scanf("%d%d", &n, &m) != EOF) {
		for (i = 0; i < n; i++)
			for (j = 0; j < n; j++)
				if (i == j)
					Edge[i][j] = 0;
				else
					Edge[i][j] = INF;
		int x, y, z;
		for (i = 0; i < m; i++) {
			scanf("%d%d%d", &x, &y, &z);
			if (z < Edge[x][y])
				Edge[y][x] = Edge[x][y] = z;
		}
		scanf("%d%d", &x, &y);
		Dijkstra(x);
		if (dist[y] < INF)
			printf("%d\n", dist[y]);
		else
			printf("-1\n");
	}//while
	return 0;
}

HDU 2544：

#include <cstdio>

#define MAXN 200
#define INF 0xfffff 

int n;
int Edge[MAXN][MAXN];
int s[MAXN];
int dist[MAXN];
int path[MAXN];

void Dijkstra(int v0) {
	int i, j, k;
	for (i = 0; i < n; i++) {
		dist[i] = Edge[v0][i];
		s[i] = 0;
		if (i != v0 && INF > dist[i])
			path[i] = v0;
		else
			path[i] = -1;
	}
	s[v0] = 1;
	dist[v0] = 0;
	for (i = 0; i < n - 1; i++) {
		int min = INF, u = v0;
		for (j = 0; j < n; j++)
			if (!s[j] && dist[j] < min){
				u = j;
				min = dist[j];
			}//if
		s[u] = 1;
		for (k = 0; k < n; k++) {
			if (!s[k] && Edge[u][k] < INF && dist[u] + Edge[u] [k] < dist[k]) {
				dist[k] = dist[u] + Edge[u][k];
				path[k] = u;
			}//if
		}//for
	}//for
}

int main() {
	int m;
	int i, j;
	while (scanf("%d%d", &n, &m) && n && m) {
		for (i = 0; i < n; i++)
			for (j = 0; j < n; j++)
				if (i == j)
					Edge[i][j] = 0;
				else
					Edge[i][j] = INF;
		int x, y, z;
		for (i = 0; i < m; i++) {
			scanf("%d%d%d", &x, &y, &z);
			if (z < Edge[x-1][y-1])
				Edge[y-1][x-1] = Edge[x-1][y-1] = z;
		}
		Dijkstra(0);
		printf("%d\n", dist[n - 1]);
	}//while
	return 0;
}