c_cpp 找到具有给定约束的矩阵中的最长路径

Posted 2021-05-14

//https://www.geeksforgeeks.org/find-the-longest-path-in-a-matrix-with-given-constraints/
#include <bits/stdc++.h>
using namespace std;

int func (int i, int j, vector < vector <int> >mat,vector < vector <int> >&dp, int n) {
    if (i<0 || i>=n || j<0 || j<=n)
        return 0;
    if (dp[i][j]!= -1)
        return dp[i][j];
    if (i>0 && mat[i-1][j]== mat[i][j]+1)
        return dp[i][j]= 1+ func(i-1,j,mat,dp, n);
    if (j>0 && mat[i][j-1]== mat[i][j]+1)
        return dp[i][j]= 1+ func(i,j-1,mat,dp, n);
    if (i<n-1 && mat[i+1][j]== mat[i][j]+1)
        return dp[i][j]= 1+ func(i+1,j,mat,dp, n);
    if (j<n-1 && mat[i][j+1]== mat[i][j]+1)
        return dp[i][j]= 1+ func(i,j+1,mat,dp, n);
    dp[i][j]= 1;
}

int main() {
    int n;
    cin>>n;
    vector < vector <int> >mat (n, vector <int> (n));
    for (int i=0;i<n;i++)
        for (int j=0;j<n;j++)
            cin>> mat[i][j];

    int ans= 0;
    vector < vector <int> >dp (n, vector <int> (n,-1));
    for (int i=0;i<n;i++) {
        for (int j=0;j<n;j++) {
            if (dp[i][j]== -1)
                func(i,j,mat, dp, n);
            ans= max(ans, dp[i][j]);
        }
    }
    cout<<ans;
}