Search a 2D Matrix II

题目：

Write an efficient algorithm that searches for a value in an m x n matrix, return the occurrence of it.

This matrix has the following properties:

Integers in each row are sorted from left to right.

Integers in each column are sorted from up to bottom.

No duplicate integers in each row or column.

Example: Consider the following matrix:

[

[1, 3, 5, 7],

[2, 4, 7, 8],

[3, 5, 9, 10]

]

分析：

这道题目的逻辑比较有意思，如果matrix[x][y]==target，那么朝右上移动，否则，< target向右，> target向上。

解法：

class Solution {
public:
    /**
     * @param matrix: A list of lists of integers
     * @param target: An integer you want to search in matrix
     * @return: An integer indicate the total occurrence of target in the given matrix
     */
    int searchMatrix(vector<vector<int> > &matrix, int target) {
        // write your code here
        if (matrix.size() == 0) {
            return 0;
        }
        if (matrix[0].size() == 0) {
            return 0;
        }

        int m = matrix.size();
        int n = matrix[0].size();

        int x = m - 1;
        int y = 0;

        int count = 0;
        while (x >=0 && y <n) {
            if (matrix[x][y] == target) {
                count++;
                x--;
                y++;
            } else if (matrix[x][y] < target) {
                y++;
            } else {
                x--;
            }
        }

        return count;
    }
};