题目
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
- Integers in each row are sorted in ascending from left to right.
- Integers in each column are sorted in ascending from top to bottom.
Example:
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
.
解法
二维矩阵的解法,注意题目是在有序的前提下:
class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
if(matrix==null||matrix.length==0||matrix[0].length==0) return false;
int row=0;
int col=matrix[0].length-1;
while(row<matrix.length&&col>=0){
int curr=matrix[row][col];
if(target==curr){
return true;
}
else if(target>curr){
row++;
}
else{
col--;
}
}
return false;
}
}