python3 解法, 执行用时: 44 ms, 内存消耗: 15.9 MB, 提交时间: 2023-05-10 10:27:19

class Solution:
    def monotoneIncreasingDigits(self, N: int) -> int:
        ones = 111111111
        result = 0
        for _ in range(9):
            while result + ones > N:
                ones //= 10
            result += ones
        return result

java 解法, 执行用时: 1 ms, 内存消耗: 38.6 MB, 提交时间: 2023-05-10 10:26:19

class Solution {
    public int monotoneIncreasingDigits(int N) {
        char[] arr = (N + "").toCharArray();
        int max = -1, idx = -1;
        for (int i = 0; i < arr.length - 1; i++) {
            if (max < arr[i]) {
                max = arr[i];
                idx = i;
            }
            if (arr[i] > arr[i + 1]) {
                arr[idx] -= 1;
                for(int j = idx + 1;j < arr.length;j++) {
                    arr[j] = '9';
                }
                break;
            }
        }
        return Integer.parseInt(new String(arr));
    }
}

golang 解法, 执行用时: 0 ms, 内存消耗: 1.9 MB, 提交时间: 2023-05-10 10:25:27

func monotoneIncreasingDigits(n int) int {
    s := []byte(strconv.Itoa(n))
    i := 1
    for i < len(s) && s[i] >= s[i-1] {
        i++
    }
    if i < len(s) {
        for i > 0 && s[i] < s[i-1] {
            s[i-1]--
            i--
        }
        for i++; i < len(s); i++ {
            s[i] = '9'
        }
    }
    ans, _ := strconv.Atoi(string(s))
    return ans
}