进阶实验1-3.1-两个有序序列的中位数-编程题

解题代码

#include<stdio.h>
#include<stdlib.h>
int Re(int a[], int left, int right, int K);
int main()
{
	int N;
	scanf("%d", &N);
	int *a = (int *)malloc((2 * N + 1) * sizeof(int));
	int i;
	for (i = 0; i < 2 * N; i++) {
		scanf("%d", &a[i]);
	}
	int median = Re(a, 0, 2 * N - 1, N + 1);
	printf("%d", median);
	return 0;
}
int Re(int a[], int left, int right, int K) {
	//int j;
	//for (j = left; j <= right; j++) {
	//	printf("%d ", a[j]);
	//}
	//printf("\n");
	int l = left, r = right;
	int e = a[l];
	int t;
	while (left <= right) {
		if (left == right&&a[left] < e) break;
		while (left <= right&&a[left] >= e) left++;
		while (right > left&&a[right] < e) right--;
		if (left < right) {
			t = a[left];
			a[left] = a[right];
			a[right] = t;
		}
	}
	t = a[left - 1];
	a[left - 1] = a[l];
	a[l] = t;
	//printf("left=%d,right=%d,l=%d,K=%d\n\n", left, right, l, K);
	if ((left - 2 - l + 1) > K - 1) {
		return Re(a, l, left - 2, K);
	} 
	else if ((left - 2 - l + 1) < K - 1)
	{
		return Re(a, left, r, K - (left - 1 - l) - 1);
	}
	else return a[left - 1];
}

测试结果

问题整理

1.干他妈的这题。
2.学会e方法排序分解数列递归求中位数。
3.注意N最小的情况。