線性表順序存儲-練習題3-逆置順序表

題目：

        以順序表做存儲結構實現線性表，實現就地逆置算法，即在原表的存儲空間將線性表(a1, a2, ..., an)逆置爲(an, ... , a2, a1).

思路：

1. 須要考慮的線性表個數的奇/偶數狀況，奇/偶數狀況不一樣，置換的步伐長度不一樣
2. 設置一箇中轉數，當作數置換時作中轉存儲

代碼：

#include <stdio.h>
#include <stdlib.h>

#define MAXSIZE 101

typedef struct {
	int r[MAXSIZE];
	int length;
} SqList;

void inverseElement(SqList *L);
void print(SqList L);
int main(int argc, char *argv[]) {
	SqList list;
	int i;
	list.length = 9;
	for (i = 1; i <= list.length; i++) {
		list.r[i] = i * 3;
	}
	printf("初始順序表：\n");
	print(list);
	printf("\n");
	inverseElement(&list);
	printf("置換後的順序表：\n");
	print(list);
	return 0;
}

/**
 *  逆置順序表
 */
void inverseElement(SqList *L) {
	int middle = 0, k = -1, i;
	if (L->length % 2 == 0) {
		for (i = L->length / 2; i > 0; i--) {
			k += 2;
			middle = L->r[i];
			L->r[i] = L->r[i + k];
			L->r[i + k] = middle;
		}
	} else {
		k = 0;
		for (i = L->length / 2; i > 0; i--) {
			k += 2;
			middle = L->r[i];
			L->r[i] = L->r[i + k];
			L->r[i + k] = middle;
		}
	}
}

void print(SqList L) {
	for (int i = 1; i <= L.length; i++) {
		printf("%d\t", L.r[i]);
	}
}