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P1083 借教室

out set bool nbsp def 經典 main () algorithm

經典題

二分 + 前綴和

註意long long 和初始化change[] //QAQ

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<algorithm>
 5 #define ll long long   //註意long long
 6 
 7 using namespace std;
 8 const int N = 1000000 + 5;
 9 ll n,m;
10 ll d[N],sum[N],c[N],a[N],b[N],change[N];
11 bool bo;
12 bool check(ll x){ 13 memset(change,0,sizeof(change)); //註意初始化QAQ 14 for(int i = 1;i <= x;++ i){ 15 change[a[i]] += c[i]; 16 change[b[i] + 1] -= c[i]; 17 } 18 ll sum = 0; 19 for(int i = 1;i <= n;++ i){ 20 sum += change[i]; 21 if(sum > d[i]) return
true; 22 } 23 return false; 24 } 25 int main(){ 26 scanf("%lld%lld",&n,&m); 27 for(int i = 1;i <= n;++ i){ 28 scanf("%lld",&d[i]); 29 } 30 for(int i = 1;i <= m;++ i){ 31 scanf("%lld%lld%lld",&c[i],&a[i],&b[i]); 32 } 33 ll l = 0
,r = m; // l :不可能,r:可能 34 while(r - l > 1){ 35 ll mid = (l + r) >> 1; 36 if(check(mid)){ 37 r = mid; 38 bo = 1; //有輸出的可能值 39 } 40 else{ 41 l = mid; 42 } 43 } 44 if(bo){ 45 cout << "-1" << \n; 46 cout << r << \n; //輸出可能值r 47 } 48 else{ 49 cout << "0" << \n; 50 } 51 return 0; 52 }

P1083 借教室