LeetCode(Java)

发现了中文版的leetCode，网址在https://leetcode-cn.com

70. 爬楼梯

题目地址：https://leetcode-cn.com/problems/climbing-stairs/submissions/
解题思路：最简单的动态规划题目，状态方程与斐波那契数列相同。

    public int climbStairs(int n) {
        if(n < 2) return n;
        int s1 = 1,s2 = 2;
        for(int i =2;i < n;i++){
            int cur = s1 + s2;
            s1 = s2;
            s2 = cur;
        }
        return s2;
    }

167. 两数之和 II - 输入有序数组

题目地址：https://leetcode-cn.com/problems/two-sum-ii-input-array-is-sorted/submissions/
解题思路：双指针法

    public int[] twoSum(int[] numbers, int target) {
        int len = numbers.length;
        int[] res = new int[2];
        if(len <=1) return res;
        int l = 0;
        int r = len -1;
        while(l < r){
            if(numbers[l] + numbers[r] == target){
                res[0] = l+1;
                res[1] = r+1;
                return res;
            }else if(numbers[l] + numbers[r] > target){
                r--;
            }else{
                l++;
            }
        }
        return res;
    }

202. 快乐数

class Solution {
    public boolean isHappy(int n) {
        if(n==7 || n==1) return true;
        if(n<10) return false;
        int sum = 0;
        while(n>=1){
            int d = n%10;
            sum+= d*d;
            n/=10;
        }
        return isHappy(sum);
    }
}

455.分发饼干

题目地址：https://leetcode-cn.com/problems/assign-cookies/submissions/
解题思路：贪心算法，从小的孩子，用小的饼干满足。

    public int findContentChildren(int[] g, int[] s) {
        Arrays.sort(g);
        Arrays.sort(s);
        int si = 0;
        int gi = 0;
        while(gi

680.验证回文字符串 Ⅱ

题目地址：https://leetcode-cn.com/problems/valid-palindrome-ii/
解题思路：正常验证回文串，如果错误，给一次复活的机会。

public boolean validPalindrome(String s) {
        int start = 0;
        int end = s.length() - 1;
        while(start