uvalibe4294 Shuffle

the main algorithm of the code:

1, find the first repeat position of the sequence, and mark it (for that once it repeat, it can never be ok)

2,use the array named ok to mark whether the sequence from i to i+s-1 is never repeat

3,check from the position i to the end to find that if the ok[i] is always true, which means that the later word is fine(= =), if so , the position of the first word can be sure as the n-i, s0 ans++

code:

#include<iostream>  
#include<cstdio>  
#include<cstring>  
using namespace std;  
  
typedef long long int64;  
  
const int INF = 0x3f3f3f3f;  
const int MAXN = 100010;  
  
int s, n;  
int arr[MAXN];  
int cnt[MAXN];  
bool first[MAXN], ok[MAXN];  

void init() {
	memset(first, 0, sizeof(first));
	memset(ok, 0, sizeof(ok));
	memset(cnt, 0, sizeof(cnt));
	first[0] = 1, ok[n] = 1;
	int i;
	for(i=0; i<s&&i<n&&!cnt[arr[i]]; i++) {
		cnt[arr[i]] = 1;
		first[i+1] = 1;
	}
	if(i==n && i<s && first[i]) {
		while(i++<s) first[i] = 1;
	}
	memset(cnt, 0, sizeof(cnt));
	ok[n] = 1;
	int count = 0;
    for(int i=n-1; i>=0; --i){  
		if(cnt[arr[i]]++ == 0) {
//cnt[arr[i]]++;//it is wrong
			
			count++;
		}

        if(count == s || n-i<s&&n-i==count){  
            ok[i] = true;  
        }  
        if(i+s-1<n){  
            if(--cnt[arr[i+s-1]] == 0){  //the word is out of consider
                --count;  
            }  
        }  
    }  
}

bool check(int st) {
	while(st<n) {
		if(!ok[st]) return false;
		st += s;
	}
	return true;
}

int main() {
	int kase;
	scanf("%d", &kase);
	while(kase--) {
		scanf("%d%d", &s, &n);
		for(int i=0; i<n; i++) {
			scanf("%d",&arr[i]);
		}
		init();
		int ans = 0;
		for(int i=0; i<s; i++) //give out all the possible position
			if(first[i] && check(i)) {
				++ans;
			}
		printf("%d\n", ans);
	}
	return 0;
}