Compare Strings

Compare two strings A and B, determine whether A contains all of the characters in B.

The characters in string A and B are all Upper Case letters.

 Notice

The characters of B in A are not necessary continuous or ordered.

Example

For A = "ABCD", B = "ACD", return true.

For A = "ABCD", B = "AABC", return false.

分析：

用array记录每个字符在A中出现的个数，然后再减去B中的字符，如果不够，说明不包含。

public class Solution {
    /**
     * @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
     */
    public boolean compareStrings(String A, String B) {
        if (A == null & B != null) return false;
        if (A == null && B == null) return true;
        if (B == null) return true;
        
        int[] charCounts = new int[256];
        
        for (int i = 0; i < A.length(); i++) {
            charCounts[A.charAt(i)]++;
        }
        
        for (int i = 0; i < B.length(); i++) {
            if (charCounts[B.charAt(i)] == 0) {
                return false;
            }
            charCounts[B.charAt(i)]--;
        }
        return true;
    }
}