Likou selected top interview questions--------Yang Hui Triangle

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Idea: This
question is a simple question. For each level, we can add 1 first, then add a certain number of values, and then add 1. You can see the code for details.

Code:

class Solution {
    
    
public:
    vector<vector<int>> generate(int numRows) {
    
    
        vector<vector<int> > ans;
        
        ans.push_back({
    
    1});
        if(numRows==1){
    
    
            return ans;
        }

        for(int i=1;i<numRows;++i){
    
    
            vector<int> q;
            q.push_back(1);
            if(q.size()!=i){
    
    
                for(int j=1;j<i;++j){
    
    
                    q.push_back(ans[i-1][j-1]+ans[i-1][j]);
                }
            }
            q.push_back(1);
            ans.push_back(q);
        }
        return ans;
    }
};