Minimum number of flips to make binary grid palindromic i

Array Two Pointers Matrix

74.8% acceptance

Feb 25, 2026

You are given an m x n binary matrix grid. A row or column is considered palindromic if its values read the same forward and backward. You can flip any number of cells in grid from 0 to 1, or from 1 to 0. Return the minimum number of cells that need to be flipped to make either all rows palindromic or all columns palindromic.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn min_flips(grid: Vec<Vec<i32>>) -> i32 {
    let m = grid.len();
    let n = grid[0].len();

    // Flips to make all rows palindromic
    let mut row_flips = 0i32;
    for r in 0..m {
      for c in 0..n / 2 {
        if grid[r][c] != grid[r][n - 1 - c] {
          row_flips += 1;
        }
      }
    }

    // Flips to make all columns palindromic
    let mut col_flips = 0i32;
    for c in 0..n {
      for r in 0..m / 2 {
        if grid[r][c] != grid[m - 1 - r][c] {
          col_flips += 1;
        }
      }
    }

    row_flips.min(col_flips)
  }
}