剑指 Offer 31. 栈的压入、弹出序列(中等)

class Solution {
public:
    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
        int n = pushed.size();
        stack<int> stk;
        int idx =0;
        for(auto it:pushed){
            stk.push(it);        
            while(!stk.empty() && popped[idx] == stk.top()){
                stk.pop();
                idx++;
            }
        }
        return stk.empty();

    }
};

剑指 Offer 16. 数值的整数次方(中等)

自己瞎写的快速幂方法

class Solution {
public:
    double myPow(double x, int n) {
        double k = x;
        double res = 1;
        if(n < 0) k =1.0/k;
        while(n){    
            if(n%2==1 || n%2 == -1){
                res = res*k;
            }
            k = k*k;
            n/=2;
        }
        return res;
    }
};

效果似乎不是很好.png

剑指 Offer 38. 字符串的排列(中等)

K神的题解一如既往的清晰明了

class Solution {
public:
    vector<string> permutation(string s) {
        dfs(s,0);
        return res;

    }
    vector<string> res;
    void dfs(string& s,int idx){
        if(idx == s.size()-1){
            res.push_back(s);
            return ;
        }
        set<int> vis;
        for(int i =idx; i < s.size(); i++){
            if(vis.count(s[i])) continue;
            vis.insert(s[i]);
            swap(s[i],s[idx]);
            dfs(s,idx+1);
            swap(s[i],s[idx]);

        }
    }

};

image.png