提交记录 #238

#include<stdio.h>
#include<string.h>
char str[150000],curstr[150000];
int vFac[20000],vExp[20000],n=0;
int main(){
    fgets(str,150000,stdin);
    char *ptr=strchr(str,'=')+1,*nxt;
    do{
        // slice the original string into substrings
        nxt=strchr(ptr,'+');
        if(nxt==NULL) nxt=ptr+strlen(ptr);
        strncpy(curstr,ptr,nxt-ptr); curstr[nxt-ptr]='\0';
        // calculate the factorial and exponent of the substring
        char *div=strchr(curstr,'x');
        if(div==NULL) vExp[n]=0,div=curstr+strlen(curstr);
        else if(*(div+1)!='^') vExp[n]=1;
        else sscanf(div+2,"%d",&vExp[n]);
        curstr[div-curstr]='\0';
        if(*curstr=='\0') vFac[n]=1;
        else sscanf(curstr,"%d",&vFac[n]);
        // move to the next substring
        ptr=nxt+1; n++;
    }while(*nxt!='\0');
    while(vExp[n-1]==0) n--; // remove trailing zeroes
    // calculate the derivative of the expression
    printf("f'(x)=");
    int ansCount=0;
    for(int i=0;i<n;i++){
        if(vExp[i]==0) continue;
        int vf=vFac[i]*vExp[i],ve=vExp[i]-1;
        if(vf==0) continue;
        if(ve==0) printf("%d",vf);
        else if(ve==1&&vf==1) printf("x");
        else if(ve==1) printf("%dx",vf);
        else if(vf==1) printf("x^%d",ve);
        else printf("%dx^%d",vf,ve);
        if(i<n-1) printf("+");
        ansCount++;
    }
    if(ansCount==0) printf("0");
    putchar('\n');
    return 0;
}