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 程式師世界 >> 編程語言 >> C語言 >> C++ >> C++入門知識 >> [LeetCode] Search a 2D Matrix

[LeetCode] Search a 2D Matrix

編輯:C++入門知識

[LeetCode] Search a 2D Matrix


 

Search a 2D Matrix

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.

解題思路:

題意為給定一個矩陣和一個目標值,判斷目標值是否在矩陣中存在。矩陣滿足:每一行從左往右遞增,後一行的第一個元素大於前一行最後一個元素。

可以考慮二分查找法,將一維坐標轉化成二維坐標即可。

 

class Solution {
public:
    bool searchMatrix(vector>& matrix, int target) {
        //二分查找,將矩陣查找轉化成線性查找
        int m = matrix.size();
        if(m==0){
            return false;
        }
        int n = matrix[0].size();
        if(n==0){
            return false;
        }
        int start = 0, end = m*n-1;
        while(start<=end){
            int middle = (start + end)/2;
            int x = middle / n;
            int y = middle % n;
            if(matrix[x][y]==target){
                return true;
            }else if(matrix[x][y]

 

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