365. Count 1 in Binary【LintCode java】

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Description

Count how many 1 in binary representation of a 32-bit integer.

Example

Given 32, return 1

Given 5, return 2

Given 1023, return 9

Challenge

If the integer is n bits with m 1 bits. Can you do it in O(m) time?

解題：很簡單，但是要考慮範圍的問題。代碼如下：

public class Solution {    /*     * @param num: An integer     * @return: An integer     */    public int countOnes(int num) {        // write your code here        int count = 0;        long temp = (long)num;        if(temp < 0){            temp = (long)Math.pow(2,32) + temp;        }        while(temp != 0){            if(temp %2 == 1)                count++;            temp = temp / 2;        }        return count;    }};

 

365. Count 1 in Binary【LintCode java】