usaco-2.3-zerosum-pass
递归,递归:
/* ID: qq104801 LANG: 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: zerosum LANG: C++ Compiling... Compile: OK Executing... 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 ---- 9 Keep up the good work! Thanks for your submission!
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看书看原版,原汁原味。
不会英文?没关系,硬着头皮看下去慢慢熟练,才会有真正收获。
没有原书,也要网上找PDF来看。
网上的原版资料多了去了,下载东西也到原始下载点去看看。
你会知其所以然,呵呵。
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