pku 2623 sequence median 水题 解题报告

pku 2623 sequence median 水题 解题报告

水题而已.但却让我提交了wa几次,需要总结下:

1.       int范围不能超过2的32次方;

2.       __int64可以用qsort,但记得修改相应的cmp;

3.       初次分析很重要,要狠且正确.

AC代码:

·                #include <stdio.h>

·                #include <stdlib.h>

·                #include <string.h>

·                #include <algorithm>

·                using namespace std;

·                 

·                __int64 a[250005];

·                 

·                int cmp(const void *a, const void *b)

·                {

·                      return *(__int64 *)a - *(__int64 *)b;

·                }

·                 

·                int main()

·                {

·                      int i;

·                      int n;

·                      scanf("%I64d", &n);

·                      for (i = 1; i <= n; i++)

·                      {

·                            scanf("%d", &a[i]);

·                      }

·                      sort(a+1, a +n+1);

·                      //qsort(a + 1, n, sizeof(a[1]), cmp);

·                      if (n % 2)

·                      {

·                            printf("%.1lf/n", (double) a[(n+1)/2]);

·                      }

·                      else

·                      {

·                            printf("%.1lf/n", (double) (a[n/2] + a[n/2+1]) / 2.0);

·                      }

·                      return 0;

·                }