#include<stdio.h>#include<string.h>int i,t=1;char a[100];
void E();void E1();void T();void T1();void F();
void E(){T();E1();}void T(){F();T1();}void E1(){if(a[i]=='+'||a[i]=='-'){i++;T();E1();}else if(a[i]=='#'||a[i]==')'){i++;}}void T1(){if(a[i]=='*'||a[i]=='/'){i++;F();T1();}else if(a[i]=='#'||a[i]==')'){i++;}
}void F(){int d;if((a[i]<='z'&&a[i]>='a')||(a[i]<='Z'&&a[i]>='A')){if((a[i++]<='z'&&a[i++]>='a')||(a[i++]<='Z'&&a[i++]>='A'))i++;else {printf("\n分析失败!\n");t=0;}}if(a[i]<='9'&&a[i]>='0'){if(a[i++]<='9'&&a[i++]>='0')i++;else {printf("\n分析失败!\n");t=0;}}else if(a[i]=='('){E();if(a[i]==')'){i++;}else{ printf("\n分析失败!\n");exit (0);}}else{ printf("\n分析失败!\n");exit (0);}}int main(){int len,d;start:printf("请输入表达式：\n");scanf("%s",a);len=strlen(a);a[len]='#';a[len+1]='\0';E();if(t==1){printf("是正确的表达式\n");}printf("是否重试？重试输入1:");scanf("%d",&d);if(d=1)goto start;return 0;
转载于:https://www.cnblogs.com/huaziyi666/p/5106102.html
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