Snake Sequence

You are given a grid of numbers. A snake sequence is made up of adjacent numbers such that for each number, the number on the right or the number below it is +1 or -1 its value.

For example
1 3 2 6 8
-9 7 1 -1 2
1 5 0 1 9

output : 3 2 1 0 1

1. Given a grid, find the longest snake sequences and their lengths (so there can be multiple snake sequences with the maximum length).

public class Solution {
    public List<List<Integer>> SnakeSequence(int[][] grid) {
        List<List<Integer>> ret = new LinkedList<List<Integer>>();
        int m = grid.length;
        int n = grid[0].length;
        int[][] dp = new int[m][n];
        int longest = 0;
        for(int i=0; i<m; i++) {
            for(int j=0; j<n; j++) {
                if(i>0 && Math.abs(grid[i-1][j]-grid[i][j])==1) {
                    dp[i][j] = Math.max(dp[i][j], dp[i-1][j]+1);
                }
                if(j>0 && Math.abs(grid[i][j-1]-grid[i][j])==1) {
                    dp[i][j] = Math.max(dp[i][j], dp[i][j-1]+1);
                }
                if(dp[i][j]>longest) {
                    longest = dp[i][j];
                }
            }
        }
        
}

 

2. What about the longest increasing(by +1) snake sequence. This time, the numbers are in an increasing order in the sequence.

For example
2 3 4 5
4 5 10 11
20 6 9 12
6 7 8 40

output : 4 5 6 7 8 9 10 11 12

//
//  main.cpp
//  TestC_cpp
//
//  Created by Joyce on 14-10-8.
//  Copyright (c) 2014年 Yang Li. All rights reserved.
//

#include <iostream>
using namespace std;

int arr[4][4] = {{2,3,4,5},{4,5,10,11},{20,6,9,12},{6,7,8,40}}; // given array.
int temp[4][4];
int M=4, N=4;

int fill(int temp[][4], int i, int j){
    if(i<0 || j<0 || i>=M || j>=N)
        return 0;
    
    if(temp[i][j] != 0)
        return temp[i][j];
    
    int left=0,right=0,up=0,down=0;
    if(arr[i-1][j] == arr[i][j] +1){ /// cpp compiler won't claim if the idx is over limit
        up = fill(temp,i-1,j);
        if(up+1>temp[i][j])
            temp[i][j] = up+1;
    }
    if(arr[i+1][j] == arr[i][j] +1) {
        down = fill(temp,i+1,j);
        if(down+1>temp[i][j])
            temp[i][j] = down+1;
    }
    if(arr[i][j-1] == arr[i][j] +1){
        left = fill(temp,i,j-1);
        if(left+1>temp[i][j])
            temp[i][j] = left+1;
    }
    if(arr[i][j+1] == arr[i][j] +1){
        right = fill(temp,i,j+1);
        if(right+1>temp[i][j])
            temp[i][j] = right+1;
    }
    return temp[i][j];
}

int main(int arg, char** args) {
    int i, j;
    for (i=0;i<M;i++){
        for(j=0;j<N;j++){
            if(temp[i][j] == 0){
                fill(temp,i,j);
            }
        }
    }
    for(i=0; i<4; i++) {
        for(j=0; j<4; j++) {
            cout<<temp[i][j];
        }
        cout<<'\n';
    }
    // find the max elem in temp
    int max_x=0, max_y=0;
    for(i=0;i<M;i++){
        for(j=0;j<N;j++){
            if(temp[i][j] > temp[max_x][max_y]){
                max_x = i;
                max_y = j; 
            } 
        } 
    }
    // find the path
    i=max_x, j= max_y ;
    cout<<arr[i][j]<<',';
    while(temp[i][j] != 0){
        if(temp[i-1][j] == temp[i][j]-1 && arr[i-1][j] == arr[i][j]+1){
            i = i-1;
            cout<<arr[i][j]<<',';
            continue;
        }
        if(temp[i+1][j] == temp[i][j]-1 && arr[i+1][j] == arr[i][j]+1){
            i = i+1;
            cout<<arr[i][j]<<',';
            continue;
        }
        if(temp[i][j-1] == temp[i][j]-1 && arr[i][j-1] == arr[i][j]+1){
            j = j-1;
            cout<<arr[i][j]<<',';
            continue; 
        } 
        if(temp[i][j+1] == temp[i][j]-1 && arr[i][j+1] == arr[i][j]+1){
            j = j+1; 
            cout<<arr[i][j]<<',';
            continue; 
        } 
    } 
}