couple

Description N couples are standing in a circle, numbered consecutively
clockwise from 1 to 2N. Husband and wife do not always stand together.
We remove the couples who stand together until the circle is empty or
we can’t remove a couple any more.

Can we remove all the couples out of the circle?

Input There may be several test cases in the input file. In each case,
the first line is an integer N(1 <= N <= 100)—-the number of
couples. In the following N lines, each line contains two integers
—- the numbers of each couple. N = 0 indicates the end of the input.

Output Output “Yes” if we can remove all the couples out of the
circle. Otherwise, output “No”.

Sample Input 4 1 4 2 3 5 6 7 8

2 1 3 2 4

6 1 12 2 11 3 10 4 9 5 6 7 8

7 1 14 4 13 2 3 5 10 12 11 6 9 7 8

0 Sample Output Yes No Yes Yes

#include <stdio.h>#define MAXn (1000*2)int s[MAXn], q[MAXn];int main() {    int a, b, n, p, i;    for (scanf("%d", &n); n > 0; scanf("%d", &n)) {        for (i = 0; i < n; ++i) {            scanf("%d%d", &a, &b);            q[a-1] = q[b-1] = i;        }        p = 0;        n *= 2;        for (i = 0; i < n; ++i)            if (p > 0 && s[p-1] == q[i])//借用一个s数组来判断是否相邻的数字相同。                --p;            else                s[p++] = q[i];        if (p > 0)//只有p小于0时，才能yes            printf("No\n");        else            printf("Yes\n");    }    return 0;}