1. CountDiv 数数有几个 Compute number of integers divisible by k in range [a..b].

package com.code;

public class Test05_1 {
public static int solution(int A, int B, int K) {

// handle 6,8,7 condition
// handle 6,11,2 condition
// handle 7,12,3 condition
if(A%K==0){
return (B-A)/K + 1;
}else{
int start = A+(K-A%K);
if(start>B){ // handle 7,8,9 condition
return 0;
}else{
return (B-start)/K+1;
}
}

}
public static void main(String[] args) {

System.out.println(solution(6, 11, 2));
System.out.println(solution(6, 8, 7));
System.out.println(solution(5, 5, 3));
System.out.println(solution(6, 7, 8));
System.out.println(solution(0, 0, 11));

}
}

/**
1. CountDiv 数数有几个
Compute number of integers divisible by k in range [a..b].

Write a function:

class Solution { public int solution(int A, int B, int K); }

that, given three integers A, B and K, returns the number of integers
within the range [A..B] that are divisible by K, i.e.:

{ i : A ≤ i ≤ B, i mod K = 0 }

For example, for A = 6, B = 11 and K = 2, your function should return 3,
because there are three numbers divisible by 2 within the range [6..11], namely 6, 8 and 10.

Assume that:

A and B are integers within the range [0..2,000,000,000];
K is an integer within the range [1..2,000,000,000];
A ≤ B.
Complexity:

expected worst-case time complexity is O(1);
expected worst-case space complexity is O(1).

*/