LeetCode 329. Longest Increasing Path in a Matrix 在二维数组中寻找最长递增序列

题目：Given an integer matrix, find the length of the longest increasing path.From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed).Example 1:

nums = [
[9,9,4],
[6,6,8],
[2,1,1]
]

Return 

4

The longest increasing path is 

[1, 2, 6, 9]

.我用的是广搜+动态规划（通俗讲是再创建一个二维数组，存储到子问题的最优解，避免重复搜索）public class Solution {public int longestIncreasingPath(int[][] matrix){if(matrix==null||matrix.length==0||matrix[0].length==0)return 0;int store[][] =new int[matrix.length][matrix[0].length];int result = 0;for(int i=0;i<matrix.length;i++){for(int j=0;j<matrix[0].length;j++){int mid = findAround(i,j,matrix,store,Integer.MAX_VALUE);result = Math.max(result, mid);}}return result;}private static int findAround(int i, int j, int[][] input, int[][] store,int last) {if(i<0||i>=input.length||j<0||j>=input[0].length||input[i][j]>=last)return 0;if(store[i][j]>0)return store[i][j];else{int mid = 0;mid = Math.max(findAround(i+1, j, input, store, input[i][j]),mid);mid = Math.max(findAround(i-1, j, input, store, input[i][j]),mid);mid = Math.max(findAround(i, j+1, input, store, input[i][j]),mid);mid = Math.max(findAround(i, j-1, input, store, input[i][j]),mid);store[i][j] = ++mid;return store[i][j];}}}

改编一下，成为微软的一道面试题，在而矩阵中找最长的连续整数子序列（如:2,3,4,.....）

更改如下：

public static int longestIncreasingPath(int[][] matrix){
if(matrix==null||matrix.length==0||matrix[0].length==0)
return 0;
int store[][] =new int[matrix.length][matrix[0].length];
int result = 0;
for(int i=0;i<matrix.length;i++){
for(int j=0;j<matrix[0].length;j++){
int mid = findAround(i,j,matrix,store,matrix[i][j]-1);
result = Math.max(result, mid);
}
}
return result;
}

private static int findAround(int i, int j, int[][] input, int[][] store,int last) {
if(i<0||i>=input.length||j<0||j>=input[0].length||input[i][j]!=last+1)
return 0;
if(store[i][j]>0)
return store[i][j];
else{
int mid = 0;
mid = Math.max(findAround(i+1, j, input, store, input[i][j]),mid);
mid = Math.max(findAround(i-1, j, input, store, input[i][j]),mid);
mid = Math.max(findAround(i, j+1, input, store, input[i][j]),mid);
mid = Math.max(findAround(i, j-1, input, store, input[i][j]),mid);
store[i][j] = ++mid;
return store[i][j];
}
}