Pascal's Triangle

最新推荐文章于 2024-07-11 10:24:20 发布

原创最新推荐文章于 2024-07-11 10:24:20 发布 · 338 阅读

0 ·

CC 4.0 BY-SA版权

Leetcode 专栏收录该内容

152 篇文章

订阅专栏

class Solution {
public:
    vector<vector<int> > generate(int numRows) {
        vector<vector<int> > res;
        if (numRows==0) return res;
        vector<int> cur(1,1);
        res.push_back(cur);
        if (numRows==1) return res;
        for (int n=1; n<numRows; n++) {
            vector<int> cur(1,1);
            for (int i=1; i<n; i++) {
                cur.push_back(res[n-1][i-1]+res[n-1][i]);
            }
            cur.push_back(1);
            res.push_back(cur);
        }
        return res;
    }
};

II:

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> res;
        res.push_back(1);
        if (rowIndex==0) return res;
        vector<int> t(rowIndex+1,1);
        vector<vector<int> > r(2,t);
        int now=1, pre=0;
        for (int n=1; n<rowIndex+1; n++) {
            for (int i=1; i<n; i++) {
                r[now][i]=r[pre][i-1]+r[pre][i];
            }
            if (n!=rowIndex) {
                if (now==1) {now=0; pre=1;}
                else {now=1; pre=0;}
            }
        }
        return r[now];
    }
};

Better Solution:

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> res;
        for (int n=0; n<rowIndex+1; n++) {
            for (int i=n-1; i>0; i--) {
                res[i]=res[i-1]+res[i];
            }
            res.push_back(1);
        }
        return res;
    }
};