Computer st of op

#include<stdio.h>
#include<stack>
using namespace std;

typedef struct{
    int index;
    int prev;
}oper;

int main()
{
    int n,m;
    scanf("%d %d",&n,&m);
    int memory[n+1];for(int i=0;i<=n;i++)memory[i] = 0;

    stack<oper> st;
    for(int i=0;i<m;i++){
        char c;
        scanf(" %c",&c);
        bool pushs = true;
        oper op;
        switch(c){
            case('='):{
                int x,y;
                scanf("%d %d",&x,&y);
                op = {x,memory[x]};
                memory[x] = y;
                break;
            }
            case('+'):{
                int x,y,z;
                scanf("%d %d %d",&x,&y,&z);
                op = {z,memory[z]};
                memory[z] = memory[x] + memory[y];
                break;
            }
            case('-'):{
                int x,y,z;
                scanf("%d %d %d",&x,&y,&z);
                op = {z,memory[z]};
                memory[z] = memory[x] - memory[y];
                break;
            }
            case('C'):{
                int x,y;
                scanf("%d %d",&x,&y);
                op = {y,memory[y]};
                memory[y] = memory[x];
                break;
            }
            case('P'):{
                int x;
                scanf("%d",&x);
                printf("%d\n",memory[x]);
                pushs = false;
                break;
            }
            case('U'):{
                int t;
                scanf("%d",&t);
                while(t--){
                    int index = st.top().index;
                    int val = st.top().prev;
                    memory[index] = val;
                    st.pop();
                }
                pushs = false;
                break;
            }
        }
        if(pushs)st.push(op);
    }
    return 0;
}