Hamburger String

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本文介绍了一个有趣的编程问题——汉堡字符串问题。顾客们排队购买汉堡，如果队列中有两人穿着相同颜色的衣服，则他们之间的顾客将被服务。文章提供了一个C++程序来计算在特定条件下可以形成的汉堡字符串数量。

Hamburger String

Time Limit: 1000ms, Special Time Limit:2500ms, Memory Limit:65536KB

Total submit users: 17, Accepted users: 15

Problem 10865 : No special judgement

Problem description

BUG is a famous burger shop. Lots of costumers wait for burgers outside the burger every morning, because those hamburgers are so unforgettable.

Costumers stand in a queue, they come one by one, the latest one join into the end.

When a costumer(A) come to the end of the queue, if there’s already someone(B), wearing the same color as him, people between them(including A and B, called Hamburger String) will be served.

Served people leave the queue immediately.

N people come one by one, given their colors, can you tell me how many Hamburger Strings are there?

Input

The first line is an integer T(T<=100).

Each case has an integer N(N<=100) in the first line.

Then N positive integers(<=20) follow, each corresponds a kind of color.

1 for red, 2 for yellow, and so on.

Output

For each case output a single integer, indicating the number of Hamburger Strings are served.

Sample Input

3
1
1
2
2 2
10
1 2 3 4 3 1 2 4 1 5

Sample Output

0
1
2

Problem Source

2011ACM国际大学生程序设计竞赛湘潭邀请赛

代码：

#include <iostream>
#include <algorithm>
#include <cstdio>
#define llt long long
using namespace std;

int a[30000];

int ans;
void dfs(int l,int r){
    if(l>=r) return ;
    for(int i=l+1;i<=r;++i){
        if(a[i]==a[l]){
            ans++;
            dfs(l+1,i-1);
            dfs(i+1,r);
            return ;
        }
    }

    dfs(l+1,r);
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--){
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;++i) scanf("%d",&a[i]);
        ans = 0;
        dfs(1,n);
        printf("%d\n",ans);
    }

    return 0;
}