做题的时候忘了 数据结构老师说的hash表了， 用二分找，还好过了， hash 表 对这题 更快一些
1 #include <iostream> 2 #include <algorithm> 3 #include <string.h> 4 #include <cstdio> 5 #include <set> 6 using namespace std; 7 const int maxn =1000000+10; 8 typedef long long LL; 9 const int MAXN=1000010; 10 const int HASH=1000007; 11 inline LL read() 12 { 13 char ch=getchar();LL x=0,f=1; 14 while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();} 15 while(ch<='9'&&ch>='0'){x=x*10+ch-'0';ch=getchar();} 16 return x*f; 17 } 18 struct HASHMAP 19 { 20 int head[HASH],next[MAXN],size; 21 LL state[MAXN]; 22 void init() 23 { 24 size=0; 25 memset(head,-1,sizeof(head)); 26 } 27 bool check(LL val) 28 { 29 int h=(val%HASH+HASH)%HASH; 30 for(int i=head[h];~i;i=next[i]) 31 if(state[i]==val)return true; 32 return false; 33 } 34 int insert(LL val) 35 { 36 int h=(val%HASH+HASH)%HASH; 37 for(int i=head[h];~i;i=next[i]) 38 { 39 if(val==state[i]) 40 return 1; 41 } 42 state[size]=val; 43 next[size]=head[h]; 44 head[h]=size++; 45 return 0; 46 } 47 }H1; 48 LL A[maxn]; 49 LL sum[maxn]; 50 int main() 51 { 52 int cas; 53 scanf("%d",&cas); 54 for(int cc =1; cc<=cas; ++cc){ 55 int n; 56 LL K; 57 scanf("%d%I64d",&n,&K); 58 bool falg=false; 59 for(int i=0; i<n; ++i){ 60 scanf("%I64d",&A[i]); 61 if(K==A[i])falg=true; 62 } 63 printf("Case #%d: ",cc); 64 if(falg){ 65 printf("Yes. "); continue; 66 } 67 H1.init(); 68 sum[n]=0; LL sig=1; 69 LL to; 70 for(int i=n-1; i>=0; i--){ 71 sum[i]=sum[ i+1 ]+A[ i ]*sig; 72 if(sig==1){ 73 to = sum[i]-K; 74 if(H1.check(to)){ 75 falg=true ; break; 76 } 77 } else{ 78 to= -(-sum[i]-K); 79 if(H1.check(to)){ 80 falg=true ; break; 81 } 82 } 83 sig*=-1; 84 H1.insert(sum[i]); 85 } 86 if(falg) 87 printf("Yes. "); 88 else printf("No. "); 89 } 90 91 return 0; 92 }