2016-08-12.md

371. Sum of Two Integers
     public class Solution {

public int getSum(int a, int b) {
    if (b == 0) {
		return a;
	}

	int cxor = a ^ b;
	int candl = (a & b) << 1;

	return getSum(cxor, candl);
}  

}

181. Employees Earning More Than Their Managers
     select e1.Name as 'Employee' from Employee e1,Employee e2 where e1.ManagerId = e2.Id and e1.Salary > e2.Salary;

182. Reverse Bits
     public class Solution {

// you need treat n as an unsigned value
public int reverseBits(int n) {
    //System.out.println(n);

	int[] arr = new int[32];
	int pos = 0;
	for (int i = 0; i < 32; i++) {
		int t = n & 1;
		arr[pos++] = t;
		n = n >> 1;

		//System.out.print(arr[i]);
	}
	//System.out.println();

	int res = 0;
	for (int i = 0; i < 32; i++) {
		res = res * 2 + arr[i];
	}
	//System.out.println(res);
	return res;
}   

}

205. Isomorphic Strings
     public class Solution {

public boolean isIsomorphic(String s, String t) {
    // 都null
	if (s == null && t == null)
		return true;
	// 其中一个null
	if (s == null || t == null)
		return false;
	// 长度不相等
	if (s.length() != t.length())
		return false;
	char[] sArr = s.toCharArray();
	char[] tArr = t.toCharArray();
	Map<String, String> map = new HashMap<String, String>();
	boolean flag = true;
	for (int i = 0; i < s.length(); i++) {
		String v = map.get(sArr[i] + "");
		if (v == null) {
			if (map.containsValue(tArr[i] + "")) {
				flag = false;
				break;
			}
			map.put(sArr[i] + "", tArr[i] + "");
		} else {
			if (!v.equals(tArr[i] + "")) {
				flag = false;
				break;
			}
		}
	}
	return flag;
}  

}

20. Valid Parentheses
    public class Solution {

    public boolean judge(char a, char b) { if (a == '[' && b == ']') return true; if (a == '(' && b == ')') return true; if (a == '{' && b == '}') return true; return false; }

    public boolean isValid(String s) { char[] arr = s.toCharArray(); Stack stack = new Stack(); for (int i = 0; i < arr.length; i++) { if (stack.isEmpty()) { stack.push(arr[i]); } else { char in = stack.peek(); boolean res = judge(in,arr[i]); if(res){ stack.pop(); }else { stack.push(arr[i]); } } } return stack.isEmpty(); }

}

60. Permutation Sequence
    public class Solution {

    public String getPermutation(int n, int k) { int[] arr = new int[n]; int mSum = 1; for(int i=0;i<n;i++){ arr[i]=i+1; mSum*=i+1; } k=k-1; StringBuilder builder = new StringBuilder(); int tSum=mSum; for(int i=n;i>0;i--){ tSum = tSum/i; int pos = k/tSum; builder.append(arr[pos]); for(int j=pos;j<i-1;j++){ arr[j]=arr[j+1]; } k=k%tSum; } return builder.toString(); }

}