AtCoder Grand Contest 010

A

很水的题, 最后全是偶数就行

    #include <cstdio>
    #include <cmath>
    #include <cstring>
    #include <vector>
    #include <algorithm>
    using namespace std;
     
    typedef long long ll;
    const int qq = 5e5 + 10;
    int num[qq];
     
    int main(){
    	int n;	scanf("%d", &n);
    	int c = 0;
    	for(int i = 0; i < n; ++i){
    		scanf("%d", num + i);
    		if(num[i] % 2 == 1)
    			c++;
    	}
    	if(c % 2 == 0)	puts("YES");
    	else puts("NO");
    	return 0;
    }

B

这题是真的神奇, 想还是想到边上去了, 神tm结论, 这样的思维题要做练习... 

题解:

传送门

#include <cstdio>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cctype>
#include <stack>
using namespace std;

typedef long long ll;
const int qq = 1e5 + 10;
ll diff[qq];
ll num[qq];
ll n;

int main(){
	scanf("%lld", &n);
	ll sum = 0;
	for(int i = 0; i < n; ++i)	scanf("%lld", num + i), sum += num[i];
	for(int i = 0; i < n - 1; ++i)
		diff[i] = num[i + 1] - num[i];
	diff[n - 1] = num[0] - num[n - 1];
	ll k = (1 + n) * n / 2;
	if(sum % k != 0){
		printf("NO\n");
		return 0;
	}
	k = sum / k;
	for(int i = 0; i < n; ++i){
		if(k == diff[i])	continue;
		ll c = k - diff[i];
		if(c < 0 || c % n != 0){
			printf("NO\n");
			return 0;
		}
	}
	printf("YES\n");
	return 0;
}