剑指offer专项突击版 ---- 第1天

class Solution {
    
    public int divide(int a, int b) {
    
        if(a == Integer.MIN_VALUE && b == -1){
    
            return Integer.MAX_VALUE;
        }
        boolean flag = false;
        if((a>0 && b > 0) || (a < 0 && b < 0)){
    
            flag = true;
        }
        if(a > 0){
    
            a = -a;
        }
        if(b > 0){
    
            b = -b;
        }
        int res = 0;
        while(a <= b){
    
            a = a - b;
            res++;
        }
        return flag == true ? res : -res;

    }
}

class Solution {
    
    public String addBinary(String a, String b) {
    
        StringBuffer ans = new StringBuffer();

        int n = Math.max(a.length(), b.length()), carry = 0;
        for (int i = 0; i < n; ++i) {
    
            carry += i < a.length() ? (a.charAt(a.length() - 1 - i) - '0') : 0;
            carry += i < b.length() ? (b.charAt(b.length() - 1 - i) - '0') : 0;
            ans.append((char) (carry % 2 + '0'));
            carry /= 2;
        }
        if (carry > 0) {
    
            ans.append('1');
        }
        ans.reverse();
        return ans.toString();
    }
}

class Solution {
    
    public int[] countBits(int n) {
    
        int[] arr = new int[n+1];
        for(int i = 0; i <= n; i++){
    
            int mid = i;
            int j = 0;
            while(mid > 0){
    
                if((mid & 1) == 1){
    
                    j++;
                }
                mid = mid >> 1;
            }
            arr[i] = j;
        }
        return arr;

    }
}