位1的个数 about pisecespeng.record.me HOT 4 CLOSED

public static int func(int n) {
    int count = 0;
    for (char c : String.valueOf(n).toCharArray())
        if ('1' == c) count++;
    return count;
}

public static int func(int n) {
    int ret = 0;
    for (int i = 0; i < 32; i++) {
        if ((n & (1 << i)) != 0) {
            ret++;
        }
    }
    return ret;
}

public static int func(int n) {
    int ret = 0;
    while (n != 0) {
        n &= n - 1;
        ret++;
    }
    return ret;
}

public static int func(int n) {
    int ret = 0;
    while (n != 0) {
        n &= n - 1;
        ret++;
    }
    return ret;
}