算法导论 · 动态规划 · Floyd所有点对之间最短距离

• 算法说明
  Floyd主要来刷新两点之间的距离，三重循环
• 源代码

#include <cstdio>
#include <algorithm>
using namespace std;

#define INF 1 << 20
#define maxn 100 + 1

int n, m, a, b, c;
int G[maxn][maxn];
void output(){
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= n; j++) {
			if(i != j) {
				if(G[i][j] == INF) printf("INF ");
				else printf(" %-3d", G[i][j]);
			}
			else printf(" 0  ");
		}
		printf("\n");
	}
	printf("\n");
}
int main() {
	freopen("2.floyd’sAlgorithmAllPairsShortestPaths.txt", "r", stdin);
	freopen("2.floyd’sAlgorithmAllPairsShortestPathsOutput.txt", "w", stdout);
	//input
	scanf("%d%d", &n, &m); //n个顶点，m条边
	for(int i = 1; i <= n; i++) fill(G[i], G[i] + n + 1, INF);
	while(m--) {
		scanf("%d%d%d", &a, &b, &c);
		G[a][b] = c;
	} 
	output();
	
	//slove
	for(int k = 1; k <= n; k++) {
		for(int i = 1; i <= n; i++) {
			for(int j = 1; j <= n; j++) {
				int ij = G[i][k] + G[k][j];
				if(G[i][j] > ij) G[i][j] = ij;
			}
		}
	}
	output();
	return 0;
}

• 输入数据
  
• 运行结果