LeetCode 1523：统计某个区间的奇数个数 - 示例：低值 8，高值 10，结果 1（答案：区间内的奇数是 9）

• 0 <= low <= high <= 10^9

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 第一种方法，直接判断奇数偶数，是奇数，计数器++；

class Solution {
    public int countOdds(int low, int high) {

    int cnt = 0;

    if(low%2!=0){
        while(low<=high){
            cnt++;
            low+=2;
        }
    }
    if(low%2==0){
        low++;
        while(low<=high){
            cnt++;
            low+=2;
        }
    }
    
    return cnt;
    }
}

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第二种，列出所有情况，high-low=0；low奇，high偶；high奇，low偶；low、high全奇全偶。

class Solution {
    public int countOdds(int low, int high) {
        int cnt = 0;
        if(high-low==0){
            if(low%2==0)return cnt;
            return cnt+1;
        }
        if(low%2==0&&high%2==0){
            cnt+=(high-low)/2;
        }else if(low%2!=0&&high%2!=0){
            cnt+=((high-low)/2+1);
        }else{
            cnt+=(high-low+1)/2;
        }
        return cnt;
    }
}

第三种，一行代码秒杀！

class Solution {
    public int countOdds(int low, int high) {
        return (high+1)/2 - low/2;
    }
}