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  • Pascal's Triangle

    帕斯卡三角形,主要考察vector的用法。

    vector<vector<int> > generate(int numRows){
        vector<vector<int> > result;
        vector<int> tmp;
        result.clear();
        tmp.clear();
        int i,j;
        if(numRows == 0)
            return result;
        else if(numRows == 1){
            tmp.push_back(1);
            result.push_back(tmp);
            return result;
        }
        else if(numRows == 2){
            tmp.push_back(1);
            result.push_back(tmp);
            tmp.push_back(1);
            result.push_back(tmp);
            return result;
        }
        else{
            tmp.push_back(1);
            result.push_back(tmp);
            tmp.push_back(1);
            result.push_back(tmp);
            for(i = 2; i < numRows; i++){
                tmp.clear();            
                tmp.push_back(1);
                for(j = 1;j<=i-1;j++){
                    tmp.push_back(result[i-1][j-1]+result[i-1][j]);
                }
                tmp.push_back(1);
                result.push_back(tmp);            
            }
        }
        return result;
    }

     上次怎么写这个麻烦,第二次写得简练许多

     1     vector<vector<int> > generate(int numRows){
     2         vector<vector<int> > res;
     3         vector<int> tmp, last;
     4         if(numRows == 0)
     5             return res;
     6         int i,j; 
     7         for(i = 0; i < numRows; i++){
     8             tmp = vector<int>(i+1, 0);
     9             tmp[0] = 1;
    10             tmp[i] = 1;
    11             for(j = 1; j < i; j++)
    12                 tmp[j] = last[j-1] + last[j];
    13             res.push_back(tmp);
    14             last = tmp;
    15         }
    16         return res;
    17     }
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  • 原文地址:https://www.cnblogs.com/waruzhi/p/3317753.html
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