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     }

 

posted on 2013-09-12 20:49  waruzhi  阅读(211)  评论(0)  编辑  收藏  举报

导航