#include <stdio.h>#include <stdlib.h>#include <ctype.h>#define BUFFSIZE 128typedef struct _exp { //Integral expression int n; //Max of order int *k;//coefficient list(array)# k[0] as constant, k[n] as x^n} Exp;void print(Exp *exp);const char *extract(const char *str, char *outbuff);Exp *makeExp(const char *str);void freeExp(Exp *exp);Exp *convert(const char *str);Exp *mul(Exp *a, Exp *b);Exp *calc(const char *expStr);int main(){ char buff[BUFFSIZE]; Exp *exp; printf("input expression Eg.(x+1)(x+3)n>"); fgets(buff, sizeof(buff)/sizeof(char), stdin); exp=calc(buff); print(exp); freeExp(exp); return 0;}void print(Exp *exp){ int i, n = exp->n; for(i=n;i>=0;--i){ int k = exp->k[i]; if(k==0)continue; if(k<0) printf("-"); if(k>0 && i!=n) printf("+"); if(k<0) k*=-1;//k=|k| if(i!=0){ if(k!=1) printf("%dx", k); else printf("x"); } if(i>1) printf("^%d", i); if(i==0) printf("%d", k); } printf("n");}const char *extract(const char *str, char *outbuff){//pull out in parenthesis to outbuff, and remove space while(isspace(*str)) ++str; if(*str==' ') return NULL; while(*str!='(')++str; while(*++str!=')') if(!isspace(*str)) *outbuff++=*str; *outbuff=' '; return ++str;}Exp *makeExp(const char *str){ Exp *exp; char buff[BUFFSIZE]; exp = (Exp*)malloc(sizeof(Exp)); exp->n = 0; exp->k = (int*)calloc(1,sizeof(int)); while(*str){ int k,n; char *p; k=(int)strtol(str, &p, 10); if(k==0){//never constant zero e.g(x+0)is invalid, valid E.g (x) if(p[0]=='-'){ k = -1; ++p; } else if(p[0]=='+') { k = 1; ++p; } else k = 1; } if(*p==' '){ exp->k[0]=k;//constant part break; } if(*p=='x'){ n = (p[1]=='^') ? (int)strtol(&p[2], &p, 10):1; if(exp->n < n){ int i; exp->k = (int*)realloc(exp->k, (n+1)*sizeof(int)); for(i=n;i>exp->n;--i) exp->k[i]=0; exp->n = n; } exp->k[n] = k; if(*p==' ' || p[1]==' ')break; else{ str = (n!=1)? p:p+1; } } else { exp->k[0]=k; str = p; } } return exp;}void freeExp(Exp *exp){ free(exp->k); free(exp);}Exp *convert(const char *str){ Exp *exp; exp=makeExp(str); return exp;}Exp *mul(Exp *a, Exp *b){ Exp *ret; int i,j; ret=(Exp*)malloc(sizeof(Exp)); ret->n = a->n + b->n; ret->k = (int*)calloc(ret->n + 1, sizeof(int)); for(i=0;i<=a->n;++i){ for(j=0;j<=b->n;++j){ ret->k[i+j] += a->k[i] * b->k[j]; } } return ret;}Exp *calc(const char *expStr){ Exp *exp; char buff[BUFFSIZE]; const char *p=expStr; exp = (Exp*)malloc(sizeof(Exp)); exp->n = 0; exp->k = (int*)malloc(sizeof(int)); *exp->k = 1; while(NULL!=(p=extract(p, buff))){ Exp *e,*wk; wk=exp; e=convert(buff); exp=mul(wk, e); freeExp(wk); freeExp(e); } return exp;}
