go 1.21, clean code
```golang []
func minDeletionSize(strs []string) int {
	n, m := len(strs), len(strs[0])
	sorted := make([]bool, n-1)
	var ret int
	for j := 0; j < m; j++ {
		var i int
		for i = 0; i < n-1; i++ {
			if !sorted[i] && strs[i][j] > strs[i+1][j] {
				ret++
				break
			}
		}
		if i < n-1 {
			continue
		}
		for i = 0; i < n-1; i++ {
			if strs[i][j] < strs[i+1][j] {
				sorted[i] = true
			}
		}
	}
	return ret
}
```
['Go']