HDU 2489Minimal Ratio Tree

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#include<stdio.h>
#include<string.h>

const int INF = 0x3f3f3f3f;
const int maxn = 22;
int mps[maxn][maxn];  // 存图; 
int mp[maxn][maxn];
int pw[maxn];  // 点权 
int vis[maxn];  //是否在新图内; 
int dis[maxn];  //第i个顶点到新图最短距离; 
int prim(int n);
int ans[maxn];
int n, m,sum1,sum2;
int p[maxn];

void dfs(int pos, int k){
	if (k == m){
		int sumt1 = prim(m);  //边权和 
		int sumt2 = 0;         //点权和 
		for (int i = 0; i < m; i++){
			sumt2 += pw[p[i]];
		}
		if (sum2 == -1 || sumt1*sum2 < sum1*sumt2){  //不可将sum1设INF判断,乘法可能会爆数据 
			sum1 = sumt1;
			sum2 = sumt2;
			for (int i = 0; i < m; i++){
				ans[i] = p[i] + 1;  //题目从1到n输入; 
			} 
		}
	}
	if (n - pos + k < m)	return;  //? 
	for (int i = pos; i < n; i++){
		p[k] = i;
		dfs(i+1,k+1);
	}
	
}
int main (){

	while (scanf("%d%d", &n, &m) != EOF && n != 0){
		memset(mp, 0, sizeof(mp));
		for (int i = 0; i < n; i++){
			scanf("%d", &pw[i]);
		}
		for (int i = 0; i < n; i++){
			for (int j = 0; j < n; j++){
				scanf("%d",&mps[i][j]);
			}
		}
		sum1 = 100000;
		sum2 = -1;
		memset(ans,0,sizeof(ans));
		dfs(0,0);
		printf("%d",ans[0]);
		for (int i = 1; i < m; i++){
			printf(" %d",ans[i]);
		}
		printf("\n");
	}
}
int prim(int n){
	int ans = 0;
	memset(vis,0,sizeof(vis));
	for (int i = 0; i < m; i++){
		for (int j = 0; j < m; j++){
			mp[i][j] = mps[p[i]][p[j]];
		}
	}
	vis[0] = 1;   //注意第一个点的初始化; 
	for (int i = 0; i < n; i++)	dis[i] = mp[0][i]; // 新图第一个点为0,初始化dis; 
	for (int i = 1; i < n; i++){  // 加入第i+1个点 
		int minn = INF ;  // 旧图到新图最短距离 
		int pos = -1;    // 旧图最近点标号; 
		for (int j = 0; j < n; j++){
			if(!vis[j] && minn > dis[j]) {
				minn = dis[j];
				pos = j;
			}
		}
		if (minn == INF) return -1;
		ans += minn;     //更新答案; 
		vis[pos] = 1;
		
		for (int j = 0; j < n; j++) {
			if (!vis[j] && mp[pos][j] < dis[j]){
				dis[j] = mp[pos][j];
			}
		}
	}
	return ans;
}

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转载自blog.csdn.net/wlh1998/article/details/76164940