usaco-2.3-zerosum-pass

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遞迴，遞迴：

/*ID: qq104801LANG: C++TASK: zerosum*/#include <iostream>#include <fstream>#include <string>#include <vector>#include <cstdio>#include <algorithm>using namespace std;int N;void dfs(int n,int sum,int curr,vector<char> path){    if(n==N)    {        if(sum+curr==0)        {            for(int i=1;i<n;++i)                cout<<i<<path[i];            cout<<N<<endl;        }    }    else    {        const int next=n+1;        path[n]=‘ ‘;        dfs(n+1,sum,curr*10+(curr>0?next:-next),path);        path[n]=‘+‘;        dfs(n+1,sum+curr,next,path);        path[n]=‘-‘;        dfs(n+1,sum+curr,-next,path);    }}void test(){        freopen("zerosum.in","r",stdin);    freopen("zerosum.out","w",stdout);    cin>>N;    vector<char> start(N,0);    dfs(1,0,1,start);}int main () {            test();            return 0;}

test data:

USER: cn tom [qq104801]TASK: zerosumLANG: C++Compiling...Compile: OKExecuting...   Test 1: TEST OK [0.011 secs, 3516 KB]   Test 2: TEST OK [0.003 secs, 3516 KB]   Test 3: TEST OK [0.003 secs, 3516 KB]   Test 4: TEST OK [0.003 secs, 3516 KB]   Test 5: TEST OK [0.003 secs, 3516 KB]   Test 6: TEST OK [0.008 secs, 3516 KB]   Test 7: TEST OK [0.011 secs, 3516 KB]All tests OK.YOUR PROGRAM (‘zerosum‘) WORKED FIRST TIME! That‘s fantastic -- and a rare thing. Please accept these special automated congratulations.Here are the test data inputs:------- test 1 ----3------- test 2 ----4------- test 3 ----5------- test 4 ----6------- test 5 ----7------- test 6 ----8------- test 7 ----9Keep up the good work!Thanks for your submission!

 

usaco-2.3-zerosum-pass