poj1659 Frogs' Neighborhood

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根据度数建立无向图(无重边)

关键词：构造法

#include<stdio.h>#include<string.h>#include<iostream>#include<math.h>#include<queue>#include<algorithm>#define maxn 50#define INF 1<<30using namespace std;int n,cas;struct node{    int id,du;}frog[maxn];int link[maxn][maxn];int cmp(node a,node b){    return a.du>b.du;}bool buildmap(){    memset(link,0,sizeof(link));    for(int i=0;i<n;i++){        sort(frog+i,frog+n,cmp);        if(frog[i].du+i>n-1) return false;//无重边        for(int j=i+1;j<=i+frog[i].du;j++){            if(!frog[j].du) return false;            frog[j].du--;            int u=frog[i].id,v=frog[j].id;            link[u][v]=1;            link[v][u]=1;        }      //  frog[i].du=0;    }    return true;}int main(){    //freopen("a.txt","r",stdin);    scanf("%d",&cas);    while(cas--){        scanf("%d",&n);        for(int i=0;i<n;i++) frog[i].id=i;        for(int i=0;i<n;i++){            scanf("%d",&frog[i].du);        }        if(buildmap()){            printf("YES\n");            for(int i=0;i<n;i++){                for(int j=0;j<n;j++){                    printf("%d ",link[i][j]);                }                printf("\n");            }        }        else printf("NO\n");        printf("\n");    }}

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