1351. Count Negative Numbers in a Sorted Matrix
Given a m x n matrix grid which is sorted in non-increasing order both row-wise and column-wise, return the number of negative numbers in grid.
Example 1:
Input: grid = [[4,3,2,-1],[3,2,1,-1],[1,1,-1,-2],[-1,-1,-2,-3]] Output: 8 Explanation: There are 8 negatives number in the matrix.
Example 2:
Input: grid = [[3,2],[1,0]] Output: 0
Example 3:
Input: grid = [[1,-1],[-1,-1]] Output: 3
Example 4:
Input: grid = [[-1]] Output: 1
Constraints:
m == grid.lengthn == grid[i].length1 <= m, n <= 100-100 <= grid[i][j] <= 100
Follow up: Could you find an
O(n + m) solution?Rust Solution
struct Solution;
impl Solution {
fn count_negatives(grid: Vec<Vec<i32>>) -> i32 {
let n = grid.len();
let m = grid[0].len();
let mut j = m;
let mut res = 0;
for i in 0..n {
while j > 0 && grid[i][j - 1] < 0 {
j -= 1;
}
res += m - j;
}
res as i32
}
}
#[test]
fn test() {
let grid = vec_vec_i32![
[4, 3, 2, -1],
[3, 2, 1, -1],
[1, 1, -1, -2],
[-1, -1, -2, -3]
];
let res = 8;
assert_eq!(Solution::count_negatives(grid), res);
let grid = vec_vec_i32![[3, 2], [1, 0]];
let res = 0;
assert_eq!(Solution::count_negatives(grid), res);
let grid = vec_vec_i32![[1, -1], [-1, -1]];
let res = 3;
assert_eq!(Solution::count_negatives(grid), res);
let grid = vec_vec_i32![[-1]];
let res = 1;
assert_eq!(Solution::count_negatives(grid), res);
}
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