[C/C++基礎]- 純C中序轉後序與純C後序求值

[C/C++基礎]- 純C中序轉後序與純C後序求值

 

本篇要分享純C中序轉後序與純C後序求值，有興趣的(C/P)同好，歡迎來(C/P)一下，哈哈 ^ ^ 。

 

純C中序轉後序_程式碼

#include <cstdlib> #include <iostream> #include <cstdio> usingnamespace std; int postfix(char*); // 中序轉後序 int priority(char); // 決定運算子優先順序 int main(int argc, char *argv[]) {     char input[80];     printf("輸入中序運算式：");     scanf("%s", input);     postfix(input);     system("PAUSE");     return EXIT_SUCCESS; } int postfix(char* infix) {     int i = 0, top = 0;     char stack[80] = {'\0'};     char op;       while(1) {         op = infix[i];           switch(op) {             case '\0':                 while(top > 0) {                     printf("%c", stack[top]);                     top--;                 }                 printf("\n");                 return 0;             // 運算子堆疊             case '(':                 if(top < (sizeof(stack) / sizeof(char))) {                     top++;                     stack[top] = op;                 }                 break;             case '+': case '-': case '*': case '/':                 while(priority(stack[top]) >= priority(op)) {                     printf("%c", stack[top]);                     top--;                 }                 // 存入堆疊                 if(top < (sizeof(stack) / sizeof(char))) {                     top++;                     stack[top] = op;                 }                 break;             // 遇 ) 輸出至 (             case ')':                 while(stack[top] != '(') {                     printf("%c", stack[top]);                     top--;                 }                 top--;  // 不輸出(                 break;             // 運算元直接輸出             default:                 printf("%c", op);                 break;         }         i++;     } }   int priority(char op) {     int p;       switch(op) {        case '+': case '-':             p = 1;             break;         case '*': case '/':             p = 2;             break;         default:             p = 0;             break;     }       return p; }

 

純C後序求值_程式碼

#include <cstdlib> #include <cstdio> #include <iostream> void evalPf(char*); double cal(double, char, double); usingnamespace std;   int main(int argc, char *argv[]) {     char input[80];     printf("輸入後序式：");     scanf("%s", input);     evalPf(input);       system("PAUSE");     return EXIT_SUCCESS; } void evalPf(char* postfix) {     double stack[80] = {0.0};     char temp[2];     char token;     int top = 0, i = 0;       temp[1] = '\0';       while(1) {         token = postfix[i];         switch(token) {             case '\0':                 printf("ans = %f\n", stack[top]);                 return;             case '+': case '-': case '*': case '/':                 stack[top-1] =                        cal(stack[top-1], token, stack[top]);                 top--;                 break;             default:                 if(top < sizeof(stack) / sizeof(float)) {                     temp[0] = postfix[i];                     top++;                     stack[top] = atof(temp);                 }                 break;         }         i++;     } } double cal(double p1, char op, double p2) {     switch(op) {         case '+':             return p1 + p2;         case '-':             return p1 - p2;         case '*':             return p1 * p2;         case '/':             return p1 / p2;     } }