[转]PAT甲级练习1101. Quick Sort (25)

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1101. Quick Sort (25)

时间限制

200 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CAO, Peng

There is a classical process named partition in the famous quick sort algorithm. In this process we typically choose one element as the pivot. Then the elements less than the pivot are moved to its left and those larger than the pivot to its right. Given N distinct positive integers after a run of partition, could you tell how many elements could be the selected pivot for this partition?

For example, given N = 5 and the numbers 1, 3, 2, 4, and 5. We have:

1 could be the pivot since there is no element to its left and all the elements to its right are larger than it;

3 must not be the pivot since although all the elements to its left are smaller, the number 2 to its right is less than it as well;

2 must not be the pivot since although all the elements to its right are larger, the number 3 to its left is larger than it as well;

and for the similar reason, 4 and 5 could also be the pivot.

Hence in total there are 3 pivot candidates.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (<= 10⁵). Then the next line contains N distinct positive integers no larger than 10⁹. The numbers in a line are separated by spaces.

Output Specification:

For each test case, output in the first line the number of pivot candidates. Then in the next line print these candidates in increasing order. There must be exactly 1 space between two adjacent numbers, and no extra space at the end of each line.

Sample Input:

51 3 2 4 5

Sample Output:

31 4 5

排序后的序列每一个都是pivot，所以比较排序前后的序列可以得到数目

#include <iostream>#include <cstdio>#include <algorithm>#include <vector>int a[100000], b[100000];using namespace std; int main() {    int n;    scanf("%d", &n);    for (int i = 0; i < n; i++) {        scanf("%d", &a[i]);        b[i] = a[i];    }    sort(a, a + n);     int v[100000];    int max = 0;    int cnt = 0;    for (int i = 0; i < n; i++) {        if(a[i] == b[i] && b[i] > max) {            v[cnt++] = b[i];        }        if (b[i] > max)            max = b[i];    }    printf("%d\n", cnt);    for(int i = 0; i < cnt; i++)        if(i == 0)            printf("%d", v[i]);        else            printf(" %d", v[i]);    printf("\n");//不加这句竟然有一个测试点没法通过。。醉了。。    return 0;}

PS. 100之后的题目就不转载了，去这个小姐姐那里看好了，真的来不及了。。。http://www.liuchuo.net/pat%E7%94%B2%E7%BA%A7%E9%A2%98%E8%A7%A3%E7%9B%AE%E5%BD%95