Submission #734122

#	Time	Username	Problem	Language	Result	Execution time	Memory
734122		racsosabe	Modsum (NOI12_modsum)	C++14	25 / 25	3 ms	468 KiB

modsum

#include <bits/stdc++.h>
using namespace std;

const int MOD = 1e9 + 7;
const int N = 100000 + 5;

int add(int a, int b){
    return (a + b) % MOD;
}

int mul(long long a, long long b){
    return (a * b) % MOD;
}

int n;
long long L[N];
long long R[N];
bool vis[N][5][5];
int memo[N][5][5];

long long get_cnt(int rem, long long l, long long r){
    while((l % 5) != rem) l++;
    while(r >= 0 and (r % 5) != rem) r--;
    return l <= r ? (r - l) / 5 + 1 : 0;
}

int DP(int pos, int sum_sq, int sum){
	if(pos == n) return ((sum_sq + 1) * (sum_sq + 1) + 4) % 5 + 1;
	if(vis[pos][sum_sq][sum]) return memo[pos][sum_sq][sum];
	int res = 0;
	for(int x = 0; x < 5; x++){
		int new_sum_sq = (sum_sq + 2 * sum * x + x * x) % 5;
		int new_sum = (sum + x) % 5;
		long long Q = get_cnt(x, L[pos], R[pos]) % MOD;
		res = add(res, mul(Q, DP(pos + 1, new_sum_sq, new_sum)));
	}
	vis[pos][sum_sq][sum] = true;
	return memo[pos][sum_sq][sum] = res;
}

int main() {
	scanf("%d", &n);
	for(int i = 0; i < n; i++) scanf("%lld %lld", L + i, R + i);
	printf("%d\n", DP(0, 0, 0));
	return 0;
}

Compilation message (stderr)

modsum.cpp: In function 'int main()':
modsum.cpp:42:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
modsum.cpp:43:34: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   43 |  for(int i = 0; i < n; i++) scanf("%lld %lld", L + i, R + i);
      |                             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 5 / 5
• Subtask 5: 5 / 5