AcWing 756. 蛇形矩阵

#include<bits/stdc++.h>
using namespace std;
const int N=110;
int a[N][N];
int n,m;
int main(){
    cin>>n>>m;
    int k=0,x=0,y=-1;
    while(k!=n*m){
        while(y+1<m&&a[x][y+1]==0){
            a[x][y+1]=++k;
            y++;
        }
        while(x+1<n&&a[x+1][y]==0){
            a[x+1][y]=++k;
            x++;
        }
        while(y-1>=0&&a[x][y-1]==0){
            a[x][y-1]=++k;
            y--;
        }
        while(x-1>=0&&a[x-1][y]==0){
            a[x-1][y]=++k;
            x--;
        }
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            cout<<a[i][j]<<" ";
        }cout<<endl;
    }
}