Leetcode and Lintcode

Digit Count

Count the number of k’s between 0 and n. k can be 0 - 9.\

Example
if n=12, k=1 in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], we have FIVE 1’s (1, 10, 11, 12)

Solution:

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class Solution {
    /*
     * param k : As description.
     * param n : As description.
     * return: An integer denote the count of digit k in 1..n
     */
    public int digitCounts(int k, int n) {
        // write your code here
        int count = 0;
        
        for (int i = 0; i <= n; i++){
            count += countK(i,k);
        }
        
        return count;
    }
    
    private int countK(int i, int k){
        if (i == 0 && k == 0)
            return 1;
            
        int count = 0;
        
        while (i > 0){
            count += i % 10 == k ? 1 : 0;
            i /= 10;
        }
        
        return count;
    }
};