题目链接

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题目描述

给定一个二维数组，其每一行从左到右递增排序，从上到下也是递增排序。给定一个数，判断这个数是否在该二维数组中。

Consider the following matrix:
[
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]

Given target = 5, return true.
Given target = 20, return false.

解题思路

这是一道比较简单的dfs题，只要在右上角（左下角）开始遍历，比target大就向左，小就向右，出界了就说明没找到

  • Java 
public class Solution {
   
    private int[][] directions = {
   {
   -1, 0}, {
   1, 0}, {
   0, 1}, {
   0, -1}};
    private int m, n;
    public boolean Find(int target, int [][] array) {
   
        if (array==null || array.length==0 || array[0].length==0) return false;
        m = array.length;
        n = array[0].length;
        return dfs(target, array, 0, n-1);
    }
    private boolean dfs( int target, int[][] array, int i, int j) {
   
        if (i<0 || i>=m || j<0 || j>=n) return false;
        if (array[i][j]==target) return true;
        else if (array[i][j] > target) return dfs(target, array, i, j-1);
        else return dfs(target, array, i+1, j);
    }
}