hdu5419 Victor and Toys
设数列s,位置为i的元素被区间覆盖的数目定义为∑s[j], j ≤ i。
则给定区间[l, r], 更新数列s,只需:
++s[l],--s[r + 1]。
http://acm.hdu.edu.cn/showproblem.php?pid=5419
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 5 using namespace std; 6 typedef __int64 LL; 7 8 const int maxn = 5e4 + 10; 9 10 int w[maxn], cnt[maxn]; 11 LL A, B; 12 int n, m; 13 14 LL gcd(LL a, LL b){ 15 if(!b) return a; 16 return gcd(b, a % b); 17 } 18 19 LL f[maxn]; 20 21 void init(){ 22 for(int i = 0; i < 3; i++) f[i] = 0; 23 f[3] = 1; 24 for(int i = 3; i < maxn; i++) f[i + 1] = f[i] * (i + 1) / (i - 2); 25 } 26 27 int main(){ 28 int T; 29 scanf("%d", &T); 30 init(); 31 while(T--){ 32 scanf("%d%d", &n, &m); 33 memset(cnt, 0, sizeof cnt); 34 for(int i = 1; i <= n; i++) scanf("%d", &w[i]); 35 for(int i = 1, p, q; i <= m; i++){ 36 scanf("%d%d", &p, &q); 37 ++cnt[p], --cnt[q + 1]; 38 } 39 for(int i = 1; i <= n; i++) cnt[i] += cnt[i - 1]; 40 B = f[m]; 41 A = 0; 42 for(int i = 1; i <= n; i++) A += (LL)w[i] * f[cnt[i]]; 43 if(!A || !B){ 44 printf("0\n"); 45 continue; 46 } 47 LL D = gcd(A, B); 48 A /= D, B /= D; 49 if(B == 1) printf("%I64d\n", A); 50 else printf("%I64d/%I64d\n", A, B); 51 } 52 return 0; 53 }