[Leetcode 74, medium] Search a 2D Matrix

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Problem:

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.

Analysis:

Solutions:

C++:

    bool searchMatrix(vector<vector<int> > &matrix, int target) {        if(matrix.empty() || matrix[0].empty() || target < matrix[0][0] || target > matrix[matrix.size() - 1][matrix[0].size() - 1])            return false;                    int start = 0, end = matrix.size() - 1;        for(; start <= end;) {            if(start == end)                break;            else if(start == end - 1) {                if(matrix[end][0] <= target)                    start = end;                                break;            } else {                int mid = (start + end) / 2;                if(matrix[mid][0] == target)                    return true;                else if(matrix[mid][0] < target)                    start = mid;                else                    end = mid;            }        }                int row = start;        start = 0;        end = matrix[row].size() - 1;        for(; start <= end;) {            if(start == end) {                if(matrix[row][start] == target)                    return true;                else                    return false;            } else if(start == end - 1) {                if(matrix[row][start] == target || matrix[row][end] == target)                    return true;                else                    break;            } else {                int mid = (start + end) / 2;                if(matrix[row][mid] == target)                    return true;                else if(matrix[row][mid] < target)                    start = mid;                else                    end = mid;            }        }                return false;    }

Java:

Python:

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