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240. 搜索二维矩阵 II #70

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Description

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240. 搜索二维矩阵 II

Description

Difficulty: 中等

Related Topics: 数组, 二分查找, 分治, 矩阵

编写一个高效的算法来搜索 _m_ x _n_ 矩阵 matrix 中的一个目标值 target 。该矩阵具有以下特性:

  • 每行的元素从左到右升序排列。
  • 每列的元素从上到下升序排列。

示例 1:

输入: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]], target = 5
输出:true

示例 2:

输入: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]], target = 20
输出:false

提示:

  • m == matrix.length
  • n == matrix[i].length
  • 1 <= n, m <= 300
  • -109 <= matrix[i][j] <= 109
  • 每行的所有元素从左到右升序排列
  • 每列的所有元素从上到下升序排列
  • -109 <= target <= 109

Solution

Language: JavaScript

/**
 * @param {number[][]} matrix
 * @param {number} target
 * @return {boolean}
 */
// 双指针 左下角
var searchMatrix = function(matrix, target) {
  if(matrix.length === 0) return false
  let row = matrix.length , col = matrix[0].length,  i = row - 1, j = 0
  while( i >= 0 && j < col ) {
      if(matrix[i][j] > target) {
          i--
      } else if(matrix[i][j] < target) {
          j++
      } else {
          return true
      }
  }
  return false
};

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