LintCode(easy)比较字符串（正确版）

class Solution {
public:
    /**
     * @param A: A string includes Upper Case letters
     * @param B: A string includes Upper Case letter
     * @return:  if string A contains all of the characters in B return true 
     *           else return false
     */
    bool compareStrings(string A, string B) {
     bool w; string a(26, '0'), b(26, '0'); int m, n;
    if (A.size() < B.size()) w=false;
    else{
        //如果B为空
        if(B=="")
        w=true;
        else{
        //循环A
        for (int i = 0; i < A.size(); i++){
            m = A[i] - 65; a[m] ++;
        }
        //循环B
        for (int i = 0; i < B.size(); i++){
            n = B[i] - 65; b[n] ++;
        }

        for (int i = 0; i < B.size(); i++){
            if (a[i]>b[i])a[i] = b[i];
            //if (b[i] == '0') b[i] = a[i];
        }//cout << a << endl << b<

        //比较
        if (a >= b){ w = true; //return w; 
        }
        else w = false;
        //  cout << w;
    }}
    return w;
    }
};