day 24 |93.复原IP地址，78.子集，90.子集II

93.复原IP地址

93. 复原 IP 地址 - 力扣（LeetCode）

class Solution {
public:
    bool validNumber(string sNumber){  // “判断是否合格”
        if(stoi(sNumber) <= 255){
            return true;
        }
        return false;
    }
    vector paths;
    void restoreIpAddresses(string s, int start, string path, int depth){
        if(start >= s.size() && depth == 4){
            paths.push_back(path);   // 符合要求
        }
        if(depth > 4){
            return;
        }
        if(path != ""){
            path += '.';
        }
        string tempPath;
        for(int i = start; i < s.size() && i < start + 3; i++){
            if(s[start] == '0'){  // 前导0
                path += '0';
                restoreIpAddresses(s, start + 1, path, depth + 1);
                break;
            }
            tempPath += s[i];
            if(validNumber(tempPath)){
                int pathSize = path.size();
                path += tempPath;
                restoreIpAddresses(s, i + 1, path, depth + 1);
                path.resize(pathSize); // 回溯
            }else{
                break;
            }
        }
    }
    vector restoreIpAddresses(string s) {
        string path;
        restoreIpAddresses(s, 0, path, 0);
        return paths;
    }
};

78.子集

78. 子集 - 力扣（LeetCode）

class Solution {
public:
    vector> results;
    void subsets(vector& nums, int start, vector &path){
        results.push_back(path);
        if(start >= nums.size()){
            return ;
        }
        for(int i = start; i < nums.size(); i++){
            path.push_back(nums[i]);
            subsets(nums, i + 1, path);
            path.pop_back();
        }
    }
    vector> subsets(vector& nums) {
        vector path;
        subsets(nums, 0, path);
        return results;
    }
};

90.子集II

90. 子集 II - 力扣（LeetCode）

class Solution {
public:
    vector> results;
    void subsets(vector& nums, int start, vector &path){
        results.push_back(path);
        if(start >= nums.size()){
            return ;
        }
        for(int i = start; i < nums.size(); i++){
            path.push_back(nums[i]);
            subsets(nums, i + 1, path);
            while(i < nums.size() - 1 && nums[i] == nums[i + 1]){
                i++;
            }
            path.pop_back();
        }
    }
    vector> subsetsWithDup(vector& nums) {
        sort(nums.begin(), nums.end());
        vector path;
        subsets(nums, 0, path);
        return results;
    }
};