43. 从 1 到 n 整数中 1 出现的次数

NowCoder

解题思路

public int NumberOf1Between1AndN_Solution(int n) {
    int cnt = 0;
    for (int m = 1; m <= n; m *= 10) {
        int a = n / m, b = n % m;
        cnt += (a + 8) / 10 * m + (a % 10 == 1 ? b + 1 : 0);
    }
    return cnt;
}

Leetcode : 233. Number of Digit One-C++JavaPython)