LintCode-365.二进制中有多少个1

public class Solution {
    /**
     * @param num: an integer
     * @return: an integer, the number of ones in num
     */
    public int countOnes(int num) {
        // write your code here
        int sum = 0;
        char[] cs = Integer.toBinaryString(num).toCharArray();
        for(int i = 0; i < cs.length; i++){
            if(cs[i] == '1'){
                sum++;
            }
        }
        return sum;
    }
};

public class Solution {
    /**
     * @param num: an integer
     * @return: an integer, the number of ones in num
     */
    public int countOnes(int num) {
        // write your code here
        int sum = 0;
        if(num < 0){
            num = num ^ 0x80000000;
            sum++;
        }
        while(num > 0){
            if(num % 2 == 1){
                sum++;
            }
            num = num>>1;
        }
        return sum;
    }
};