_31.cpp

class Solution {
public:
    void nextPermutation(vector<int>& nums) {
    
        int i1,i2;
        bool hasPermutation = false;
        for(int i=nums.size()-1;i>0;i--){
            if(nums[i-1]<nums[i]){
                i1 = i-1;
                i2 = i;
                hasPermutation = true;
                break;
            }
        }
        
        if(hasPermutation){
            int j=i2;
            for(int i=nums.size()-1;i>i1;i--){
                if(nums[i]>nums[i1]){
                    j=i;
                    break;
                }
            }
            swap(nums[i1],nums[j]);
            reverse(nums.begin()+i1+1,nums.end());
        }else{
            sort(nums.begin(),nums.end());
        }
        for(auto i:nums){
            cout << i << " ";
        }
    }
};