[leetcode]240. Search a 2D Matrix II

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 in ascending from left to right.

Integers in each column are sorted in ascending from top to bottom.

For example,

Consider the following 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]
]

Given target =

5

, return

true

.

Given target =

20

, return

false

.

Solution:

matrix[row][col]从右上角开始，向左下角移动。matrix[row][col] > target, 说明col列不存在target, matrix[row][col] < target， 说明row行不存在target

bool searchMatrix(int** matrix, int matrixRowSize, int matrixColSize, int target)
{
int row = 0;
int col = matrixColSize - 1;

while ((row < matrixRowSize) && (col >= 0))
{
if (matrix[row][col] == target)
return true;
else if (matrix[row][col] > target)
col--;
else
row++;
}

return false;
}