HDU 5944 Fxx and string (暴力)

题意：给定一个字符串，问有多少个三元组满足 i, j, k组成一个等比数列，并且s[i] = 'y', s[j] = 'r', s[k] = 'x'，且j/i ,j/k中至少一个是整数。

析：直接暴力，枚举j，然后去确定 i， k，注意这个 i，k不一定谁大，谁小。

代码如下：

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>
#include <vector>
#include <map>
#include <cctype>
#include <cmath>
#include <stack>
//#include <tr1/unordered_map>
#define freopenr freopen("in.txt", "r", stdin)
#define freopenw freopen("out.txt", "w", stdout)
using namespace std;
//using namespace std :: tr1;

typedef long long LL;
typedef pair<int, int> P;
const int INF = 0x3f3f3f3f;
const double inf = 0x3f3f3f3f3f3f;
const LL LNF = 0x3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int maxn = 1e4 + 5;
const LL mod = 10000000000007;
const int N = 1e6 + 5;
const int dr[] = {-1, 0, 1, 0, 1, 1, -1, -1};
const int dc[] = {0, 1, 0, -1, 1, -1, 1, -1};
const int hr[]= {-2, -2, -1, -1, 1, 1, 2, 2};
const int hc[]= {-1, 1, -2, 2, -2, 2, -1, 1};
const char *Hex[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};
inline LL gcd(LL a, LL b){  return b == 0 ? a : gcd(b, a%b); }
int n, m;
const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
inline int Min(int a, int b){ return a < b ? a : b; }
inline int Max(int a, int b){ return a > b ? a : b; }
inline LL Min(LL a, LL b){ return a < b ? a : b; }
inline LL Max(LL a, LL b){ return a > b ? a : b; }
inline bool is_in(int r, int c){
    return r >= 0 && r < n && c >= 0 && c < m;
}
char s[maxn];

int main(){
    int T;  cin >> T;
    while(T--){
        scanf("%s", s+1);
        int len = strlen(s+1);
        int cnt = 0;
        for(int i = 1; i <= len; ++i)  if(s[i] == 'r'){
            for(int j = 2; i*j <= len ; ++j) if(i % j == 0){
                int y = i / j;
                int z = i * j;
                if(s[y] == 'y' && s[z] == 'x')  ++cnt;
                else if(s[y] == 'x' && s[z] == 'y')  ++cnt;
            }
        }
        printf("%d\n", cnt);
    }
    return 0;
}

 

青年理论计算机科学家Fxx得到了一个只包含小写字母的字符串。

字符串的长度为$n$，下标从1开始，第$i$位的字母为si\:s_is​i​​，现在Fxx想知道有多少三元组$(i,j,k)$满足下列条件

1、$i,j,k$三个数成等比数列

2、si=s_i=s​i​​='$y$',sj=,s_j=,s​j​​='$r$',sk=,s_k=,s​k​​='$x$'

3.$i/j$和$k/j$中必须有整数