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位运算计数(day2)

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题目: 求整数的2进制表示中1的个数

整数 右移 相与

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int function1(int i) {
    int count = 0;
    while(i) {
        if(i & 1)
            count ++;
        i = i >> 1;
    }
    return count;
}

flag 左移 相与

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int function2(int i) {
    int count = 0;
    unsigned int flag = 1;
    while(flag){
        if(i & flag){
            count ++;
        }
        flag = flag << 1;
    }
    return count;
}

减一相与

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int function3(int i) {
    int count = 0;
    while (i) {
        ++ count;
        i = (i - 1) & i;
    }
    return count;
}

源码github