[数据结构与算法]数据结构-中缀式转后缀式-C语言实现

数据结构-中缀式转后缀式-C语言实现

#include<stdio.h>
#include<stdlib.h>
int length(char String[]) {
	int count = 0;
	for (int i = 0; String[i] != '\0'; i++)
		count++;
	return count;
}
void after(char String[]) {
	int len = length(String);
	char stack[19];
	//char *stack = (char *)malloc(sizeof(char)*len);
	char ch[6] = { '+','-','*','/','(',')' };
	int top = -1;
	for (int i = 0; i < len; i++) {
		//printf("c:%c\n", String[i]);
		int flag = 0;//判断是否是字母还是运算符
		for (int j = 0; j < 6; j++) {
			if (String[i] == ch[j]) {
				flag = 1;
				break;
			}
		}
		//printf("%d\n", flag);
		if (flag == 0) {
			printf("%c", String[i]);
			continue;
		}
		else {
			if (String[i] == ')') {//(*)内容全部出栈
				for (; stack[top] != '('; top--) {
					printf("%c", stack[top]);
				}
				top--;
				//printf("%d\n", top);
				continue;
			}
			if (top == -1 || String[i] == '(') {
				stack[++top] = String[i];
				continue;
			}
			else {
				if (stack[top] == '(') {
					stack[++top] = String[i];
					continue;
				}

				int pr, pp;//pr表示字符当前状态,pp表示栈顶状态,用数字表示-+为0，*/为1
				if (String[i] == '+' || String[i] == '-') {
					pr = 0;
				}
				if (String[i] == '*' || String[i] == '/') {
					pr = 1;
				}
				if (stack[top] == '+' || stack[top] == '-') {
					pp = 0;
				}
				if (stack[top] == '*' || stack[top] == '/') {
					pp = 1;
				}
				if (pr <= pp) {
					int cc = 0;
					for (int j = 0; j <=top; j++)
						if (stack[j] == '(') {
							cc = 1; break;
						}
					if (cc == 1) {
						for (; stack[top] != '('; top--)
							printf("%c", stack[top]);
					}
					else
					{
						for (; top >= 0; top--)
							printf("%c", stack[top]);
					}
					stack[++top] = String[i];
				}
				else {
					stack[++top] = String[i];
				}
			}
		}
	}
	for (; top != -1; top--) {
		printf("%c", stack[top]);
	}
}
void main()
{
	char String[] = "a+b-a*((c+d)/e-f)+g";
	after(String);
}

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