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.For 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
.
這道題是經典題, 我在微軟和YELP的onsite和電面的時候都遇到了.
從右上角開始, 比較target 和 matrix[i][j]的值. 如果小於target, 則該行不可能有此數, 所以i++; 如果大於target, 則該列不可能有此數, 所以j--. 遇到邊界則表明該矩陣不含target.
[CODE]
public class Solution { public boolean searchMatrix(int[][] matrix, int target) { if(matrix.length==0 || matrix[0].length==0) return false; int i=0, j=matrix[0].length-1; while(i=0) { int x = matrix[i][j]; if(target == x) return true; else if(target < x) --j; else ++i; } return false; } }