题目链接->点击 思路：找到一个当前为0且左边是1的点，这个点一定在圈内，以这个点开始BFS进行染色。
#include<bits/stdc++.h> using namespace std; #define sd(n) scanf("%d",&n) #define sdd(n,m) scanf("%d%d",&n,&m) #define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k) #define pd(n) printf("%d\n", (n)) #define pdd(n,m) printf("%d %d\n", n, m) #define pld(n) printf("%lld\n", n) #define pldd(n,m) printf("%lld %lld\n", n, m) #define sld(n) scanf("%lld",&n) #define sldd(n,m) scanf("%lld%lld",&n,&m) #define slddd(n,m,k) scanf("%lld%lld%lld",&n,&m,&k) #define sf(n) scanf("%lf",&n) #define sff(n,m) scanf("%lf%lf",&n,&m) #define sfff(n,m,k) scanf("%lf%lf%lf",&n,&m,&k) #define rep(i,a,n) for (int i=a;i<=n;i++) #define per(i,n,a) for (int i=n;i>=a;i--) #define mm(a,n) memset(a, n, sizeof(a)) #define read std::ios::sync_with_stdio(false) typedef long long ll; int n; const int maxn=1e2+10; int a[maxn][maxn]; struct node{ int x,y; node(){} node(int x,int y){ this->x=x; this->y=y; } }; int dir[4][2]={{1,0},{-1,0},{0,1},{0,-1}}; bool book[maxn][maxn]; void bfs(int x,int y){ mm(book,false); a[x][y]=2; book[x][y]=true; queue<node>q; while(!q.empty()){ q.pop(); } q.push(node(x,y)); while(!q.empty()){ node temp=q.front(); for(int i=0;i<4;i++){ int tx=temp.x+dir[i][0]; int ty=temp.y+dir[i][1]; if(tx<1||tx>n||ty<1||ty>n)continue; if(book[tx][ty])continue; if(a[tx][ty]==0){ q.push(node(tx,ty)); book[tx][ty]=true; a[tx][ty]=2; } } q.pop(); } } int main(){ while(cin>>n){ int x,y; bool yes=false; for(int i=1;i<=n;i++){ int hasone=0; for(int j=1;j<=n;j++){ cin>>a[i][j]; if(a[i][j]==1)hasone++; else if(a[i][j]==0&&hasone==1&&!yes){ x=i;y=j; yes=true; } } } bfs(x,y); for(int i=1;i<=n;i++){ for(int j=1;j<=n;j++){ cout<<a[i][j]<<" "; } cout<<endl; } } return 0; }