[dp] hdu 2859

题目

看看最多有多长的关于对角线对称的矩阵长度
http://acm.hdu.edu.cn/showproblem.php?pid=2859

思路

从左下往右上dp

代码

#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<cctype>
#include<ctime>
#include<iostream>
#include<string>
#include<map>
#include<queue>
#include<stack>
#include<set>
#include<vector>
#include<iomanip>
#include<list>
#include<bitset>
#include<sstream>
#include<fstream>
#include<complex>
#include<algorithm>
#if __cplusplus >= 201103L
#include <unordered_map>
#include <unordered_set>
#endif
#define ll long long
using namespace std;
const int INF = 0x3f3f3f3f;
char c[1010][1010];
int dp[1010][1010];
int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int n;
	while(cin>>n){
		if(n==0) break;
		for(int i=1;i<=n;i++){
			for(int j=1;j<=n;j++){
				cin>>c[i][j];
			}
		}
		int ans=1;
		for(int i=1;i<=n;i++){
			for(int j=1;j<=n;j++){
				if(i==1||j==n){
					dp[i][j]=1;
					continue;
				}
				int x=i,y=j;
				while(x>=1&&y<=n&&c[x][j]==c[i][y]){
					x--;
					y++;
				}
				x=i-x;
				if(x>=dp[i-1][j+1]+1){
					dp[i][j]=dp[i-1][j+1]+1;
				}
				else dp[i][j]=x;
				ans=max(ans,dp[i][j]);
			}
		}
		cout<<ans<<endl;
	}
    return 0;
}