版权声明:欢迎转载,若转载,请标明出处,如有错误,请指点,也欢迎大佬们给出优化方法 https://blog.csdn.net/Charles_Zaqdt/article/details/87612465
题目链接:http://poj.org/problem?id=1985
题意是给了n个点m条边,求任意两点间的最大值。
这道题的题意感觉描述的不清楚,而且还没有数据范围...就是一道裸的求树的直径的题,输入的那个NSWD没用...
AC代码:
#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#define maxn 500005
#define inf 0x3f3f3f3f
using namespace std;
struct Node{
int to,next,w;
}Edge[maxn];
int head[maxn],num;
bool vis[maxn];
int dist[maxn];
int n,m;
void init(){
for(int i=0;i<=n;i++){
head[i] = -1;
}
num = 0;
}
void add(int u,int v,int w){
Edge[num].to = v;
Edge[num].w = w;
Edge[num].next = head[u];
head[u] = num ++;
}
void bfs(int x){
queue<int> q;
memset(dist,0,sizeof(dist));
memset(vis,false,sizeof(vis));
q.push(x);
while(!q.empty()){
int u = q.front();
q.pop();
vis[u] = true;
for(int i=head[u];i!=-1;i=Edge[i].next){
int to = Edge[i].to;
if(vis[to] == false){
vis[to] = true;
dist[to] = dist[u] + Edge[i].w;
q.push(to);
}
}
}
}
int main()
{
scanf("%d%d",&n,&m);
init();
char str[5];
for(int i=0;i<m;i++){
int u, v, w;
scanf("%d%d%d%s",&u,&v,&w,str);
add(u, v, w);
add(v, u, w);
}
bfs(1);
int pos = 0;
int Max = 0;
for(int i=1;i<=n;i++){
if(Max < dist[i]){
Max = dist[i];
pos = i;
}
}
bfs(pos);
int ans = 0;
for(int i=1;i<=n;i++){
ans = max(ans, dist[i]);
}
printf("%d\n", ans);
return 0;
}