一个简单的线段树；
被我看错题了，浪费一个半小时；
1 #include<cstdio> 2 #define maxn 500005 3 using namespace std; 4 5 struct tree 6 { 7 int l,r,value; 8 tree *right,*left; 9 }tr[maxn]; 10 int nonocount; 11 int ans; 12 13 void build(tree *rt,int l,int r) 14 { 15 rt->l=l; 16 rt->r=r; 17 if(l==r) 18 { 19 scanf("%d",&rt->value); 20 if(rt->value>0)rt->value=1; 21 else if(rt->value==0)rt->value=0; 22 else rt->value=-1; 23 return; 24 } 25 nonocount++; 26 rt->left=tr+nonocount; 27 nonocount++; 28 rt->right=tr+nonocount; 29 int mid=(l+r)>>1; 30 build(rt->left,l,mid); 31 build(rt->right,mid+1,r); 32 rt->value=(rt->left->value)*(rt->right->value); 33 } 34 35 void insert(tree *rt,int p,int x) 36 { 37 if(rt->l==p&&rt->r==p) 38 { 39 rt->value=x; 40 if(rt->value>0)rt->value=1; 41 else if(rt->value==0)rt->value=0; 42 else rt->value=-1; 43 return; 44 } 45 int mid=(rt->r+rt->l)>>1; 46 if(p<=mid)insert(rt->left,p,x); 47 else insert(rt->right,p,x); 48 rt->value=(rt->left->value)*(rt->right->value); 49 } 50 51 void query(tree *rt,int l,int r) 52 { 53 if(l==rt->l&&r==rt->r) 54 { 55 ans=ans*(rt->value); 56 return; 57 } 58 int mid=(rt->l + rt->r)/2; 59 if(r<=mid)query(rt->left,l,r); 60 else if(l>mid)query(rt->right,l,r); 61 else 62 { 63 query(rt->left,l,mid); 64 query(rt->right,mid+1,r); 65 } 66 } 67 68 char s[10]; 69 int main() 70 { 71 // freopen("in.txt","r",stdin); 72 int n,k,a,b; 73 while(scanf("%d%d",&n,&k)!=EOF) 74 { 75 nonocount=0; 76 build(tr,1,n); 77 for(int i=0;i<k;i++) 78 { 79 scanf("%s",&s); 80 if(s[0]=='C') 81 { 82 scanf("%d%d",&a,&b); 83 insert(tr,a,b); 84 } 85 else if(s[0]=='P') 86 { 87 ans=1; 88 scanf("%d%d",&a,&b); 89 query(tr,a,b); 90 if(ans==0)printf("0"); 91 else if(ans>0)printf("+"); 92 else if(ans<0)printf("-"); 93 } 94 } 95 puts(""); 96 } 97 return 0; 98 }