回溯法应用：整数拆分

题目

笔试的时候遇到这么一个问题：

6 = 1+1 +1+ 1+ 1 +1
6 = 1+ 1+ 1+ 1+ 2
6 = 1+ 1+ 1+ 3
6 = 1+ 1+ 2+ 2
6 = 1+ 1+ 4
6 = 1+ 2+ 3
6 = 1+ 5
6 = 2+ 2+ 2
6 = 2+ 4
6 = 3+ 3
6 = 6

就这样，给定一个数，打印出这种形式

分析

递归，回溯。

代码

#include<iostream>#include<vector>using namespace std;void print(int n, vector<int> &re){    if(n < 0)        return;    if(n == 0){        for(auto i : re){            cout << i << " ";        }        cout << endl;    }    else{        int start = 1;        int length = re.size();        if(length != 0)            start = re.at(length - 1);        for(int i = start; i <= n; i++){            re.push_back(i);            print(n - i, re);            re.pop_back();        }    }}int main(){    vector<int> re;    print(6, re);    return 0;}