LeetCode——Search a 2D Matrix
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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 from left to right.
- The first integer of each row is greater than the last integer of the previous row.
For example,
Consider the following matrix:
[ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ]
Given target = 3
, return true
.
原题链接:https://oj.leetcode.com/problems/search-a-2d-matrix/
题目:在m * n 的矩阵中查找目标值是否存在。
比較好的办法就是二分查找。即将矩阵总体看成一个数组来处理。
public boolean searchMatrix(int[][] matrix, int target) { if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return false; int m = matrix.length; int n = matrix[0].length; int start = 0; int end = m * n - 1; while (start <= end) { int mid = (start + end) / 2; int x = mid / n; int y = mid % n; if (matrix[x][y] == target) return true; if (matrix[x][y] < target) start = mid + 1; else end = mid - 1; } return false; }
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