Va 586 Instant Complexity

Idea: recursive Simulation

Analysis:
1. The question is the ball time complexity of a given piece of program code.
2 According to the question, we can use the stack and recursive methods, but the stack method is not easy to write, so we use recursive ideas to write
3. When we encounter LOOP, we will go recursive. When we encounter OP, we will calculate the complexity of the current layer and retuen the END time.
4. Pay attention to the final output.

Code:

 

#include<vector>#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int MAXN = 15;int ans[MAXN];char str[MAXN];void getAns(vector<string>v , int x){    int size = v.size();    int num_n = 0;    int num_xishu = x;    for(int i = 0 ; i < size ; i++){        int len = v[i].size();        if(v[i][0] == 'n')            num_n++;        else{            int sum = 0;            for(int j = 0 ; j < len ; j++)                 sum = sum*10 + v[i][j]-'0';            num_xishu *= sum;        }    }    ans[num_n] += num_xishu;}void solve(vector<string>v){    int x;    while(1){        scanf("%s" , str);        if(str[0] == 'L'){            scanf("%s" , str);             v.push_back(str);             solve(v);            v.pop_back();        }        else if(str[0] == 'O'){            scanf("%d" , &x);             getAns(v , x);        }        else if(str[0] == 'E'){            return;        }    }}void output(){    printf("Runtime = ");    bool isFirst = true;    bool isTime = false;    for(int i = MAXN-1 ; i >= 1 ; i--){        if(ans[i]){            isTime = true;             if(isFirst)                isFirst = false;            else                printf("+");            if(ans[i] > 1)                printf("%d*" , ans[i]);             printf("n");            if(i > 1)                printf("^%d" , i);        }    }    if(ans[0]){        isTime = true;         if(!isFirst)            printf("+");        printf("%d" , ans[0]);    }    if(!isTime)        printf("0");    printf("\n\n");}int main(){    int Case , cas = 1;    vector<string>v;    scanf("%d" , &Case);    while(Case--){        scanf("%s" , str);         memset(ans , 0 , sizeof(ans));        printf("Program #%d\n" , cas++);        v.clear();        solve(v);        output();    }     return 0;}