5.8 LeetCode

class Solution {
    public int titleToNumber(String s) {
        int res=0;
        for(int i=0;i<s.length();i++){
            res*=26;
            res+=(s.charAt(i)-'A'+1);
        }
            
        return res;
    }
}

class Solution {
    public double myPow(double x, int n) {
        double res = 1.0;
        for(int i = n; i != 0; i /= 2){
            if(i % 2 != 0){
                res *= x;
            }
            x *= x;
        }
        return  n < 0 ? 1 / res : res;
    }
}

class Solution {
    public int divide(int dividend, int divisor) {
        boolean flag=(dividend>=0&&divisor>0)||(dividend<=0&&divisor<0);
        int res=0;
        long m=Math.abs((long)dividend);
        long n=Math.abs((long)divisor);
        int i=31;
        while(i>=0&&res<=Integer.MAX_VALUE){
            if((m>>i)>=n){
                res+=1<<i;
                m-=n<<i;
            }
                
            i--;
        } 
         if(res==Integer.MIN_VALUE&&flag)
            return Integer.MAX_VALUE;
        if(res==Integer.MIN_VALUE&&!flag)
            return Integer.MIN_VALUE;
        if(flag) return res; 
        return -res;
    }
}