search-a-2d-matrix-ii

http://www.lintcode.com/zh-cn/problem/search-a-2d-matrix-ii/

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.empty()) {
            return 0;
        }
        int rows = matrix.size();
        int cols = matrix.at(0).size();
        
        int sum = 0;
        if(rows>0 && cols >0) {
            int row = 0;
            int col = cols-1;
            while(row < rows && col >= 0) {
                if(matrix.at(row).at(col) > target) {
                    col--;
                } else if(matrix.at(row).at(col) < target) {
                    row++;
                } else if(matrix.at(row).at(col) == target) {
                    sum++;
                    if(row < rows) row++;
                }
            }
        }
        return sum;
    }
};