ZOJ 1246 Instant Complexity(栈应用)

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计算程序时间复杂度的

有可能出现 loop 0的情况

所以给每一个块带一个coe系数,块中如果内嵌块,则把外面的块的coe系数传递过去.

#include <iostream>#include <cstdio>#include <memory.h>#include <vector>#include <string>using namespace std;#define pb push_backconst int maxn=11;bool poly[maxn];int coe[maxn];string buf;struct BLOCK{string bName;int nTimes,cons,coef;BLOCK(const string &bbName="",int nnTimes=0,int ccons=0){bName=bbName,nTimes=nnTimes,cons=ccons;coef=1;}};vector<BLOCK> stak;int main(){int t,cas=1;scanf("%d",&t);while (t--){int f=0;memset(coe,0,sizeof(coe));memset(poly,0,sizeof(poly));while (1){cin>>buf;if(buf=="BEGIN"){BLOCK b(buf);stak.push_back(b);}else if(buf=="LOOP"){char ch;cin>>ch;BLOCK b(buf);if(ch=='n'){b.nTimes=stak.back().nTimes+1;b.coef=stak.back().coef;}else{cin.putback(ch);int tm;cin>>tm;b.nTimes=stak.back().nTimes;b.coef=stak.back().coef*tm;}stak.push_back(b);}else if(buf=="OP"){int tm;cin>>tm;stak.back().cons+=tm;}else if(buf=="END"){BLOCK t=stak.back();stak.pop_back();poly[t.nTimes]=1;coe[t.nTimes]+=t.coef*t.cons;if(t.bName=="BEGIN")break;}}printf("Program #%d\nRuntime = ",cas++);int cnt=0;for (int i=maxn-1;i>=0;--i){if(coe[i]&&poly[i]){if(cnt>0)printf("+");if(i==0&&coe[i]&&poly[i]){printf("%d",coe[i]);}else if(i==1&&coe[i]&&poly[i]){if(coe[i]>1)printf("%d*n",coe[i]);elseprintf("n");}else if(coe[i]&&poly[i]){if(coe[i]>1)printf("%d*n^%d",coe[i],i);elseprintf("n^%d",i);}cnt++;f=1;}}if(f==0){printf("0\n");}else{printf("\n");}printf("\n");}return 0;}