uva 1400 - "Ray, Pass me the dishes!"
又是一道线段树区间更新的题；
1 #include<cstdio> 2 #include<algorithm> 3 #include<cstring> 4 #define ll long long 5 #define maxn 500005 6 using namespace std; 7 ll sum[maxn]; 8 struct tree 9 { 10 int l,r; 11 int ml,mr; 12 int pre,suf; 13 tree *left,*right; 14 } tr[maxn*2]; 15 16 int trcount; 17 18 void build(tree *root,int l,int r) 19 { 20 root->l=l; 21 root->r=r; 22 if(l==r) 23 { 24 root->ml=l; 25 root->mr=r; 26 root->pre=l; 27 root->suf=r; 28 return; 29 } 30 trcount++; 31 root->left=tr+trcount; 32 trcount++; 33 root->right=tr+trcount; 34 int mid=(l+r)/2; 35 build(root->left,l,mid); 36 build(root->right,mid+1,r); 37 38 //update the pre 39 if((sum[root->left->pre]-sum[root->l-1])>=(sum[root->right->pre]-sum[root->l-1])) 40 root->pre=root->left->pre; 41 else root->pre=root->right->pre; 42 //update the suf 43 if((sum[root->r]-sum[root->left->suf-1])>=(sum[root->r]-sum[root->right->suf-1])) 44 root->suf=root->left->suf; 45 else root->suf=root->right->suf; 46 //update the max 47 if((sum[root->left->mr]-sum[root->left->ml-1])>=(sum[root->right->mr]-sum[root->right->ml-1])) 48 { 49 root->ml=root->left->ml; 50 root->mr=root->left->mr; 51 } 52 else 53 { 54 root->mr=root->right->mr; 55 root->ml=root->right->ml; 56 } 57 //update the max 58 if((sum[root->mr]-sum[root->ml-1])<(sum[root->right->pre]-sum[root->left->suf-1])) 59 { 60 root->mr=root->right->pre; 61 root->ml=root->left->suf; 62 } 63 else if((sum[root->mr]-sum[root->ml-1])==(sum[root->right->pre]-sum[root->left->suf-1])) 64 { 65 if(root->left->suf<root->ml||(root->left->suf==root->ml&&root->right->pre<root->mr)) 66 { 67 root->mr=root->right->pre; 68 root->ml=root->left->suf; 69 } 70 } 71 } 72 73 void query(tree *root,int ql,int qr,int &x,int &y,int &ansl,int &ansr) 74 { 75 if((ql<=root->l)&&(root->r<=qr)) 76 { 77 x=root->ml; 78 y=root->mr; 79 ansl=root->pre; 80 ansr=root->suf; 81 return; 82 } 83 int mid=(root->r+root->l)>>1; 84 if(qr<=mid)query(root->left,ql,qr,x,y,ansl,ansr); 85 else if(ql>=mid+1)query(root->right,ql,qr,x,y,ansl,ansr); 86 else 87 { 88 int x1,x2,y1,y2,pre1,pre2,suf1,suf2; 89 90 query(root->left,ql,mid,x1,y1,pre1,suf1); 91 query(root->right,mid+1,qr,x2,y2,pre2,suf2); 92 93 ansl=(sum[pre1]-sum[root->l-1])>=(sum[pre2]-sum[root->l-1])?pre1:pre2; 94 ansr=(sum[root->r]-sum[suf1-1])>=(sum[root->r]-sum[suf2-1])?suf1:suf2; 95 96 if((sum[y1]-sum[x1-1])>=(sum[y2]-sum[x2-1])) 97 { 98 x= x1; 99 y= y1; 100 } 101 else 102 { 103 x= x2; 104 y= y2; 105 } 106 if((sum[pre2]-sum[suf1-1])>(sum[y]-sum[x-1])) 107 { 108 x= suf1; 109 y= pre2; 110 } 111 else if((sum[pre2]-sum[suf1-1])==(sum[y]-sum[x-1])) 112 { 113 if((suf1<x)||((suf1==x)&&(pre2<y))) 114 { 115 x = suf1; 116 y = pre2; 117 } 118 } 119 } 120 } 121 122 123 int main() 124 { 125 int n,q,ca=1; 126 while(scanf("%d%d",&n,&q)!=EOF) 127 { 128 ll x; 129 trcount=0; 130 memset(sum,0,sizeof sum); 131 for(int i=1; i<=n; i++) 132 { 133 scanf("%lld",&x); 134 sum[i]=sum[i-1]+x; 135 } 136 build(tr,1,n); 137 int a,b,ans1,ans2,xx,yy; 138 printf("Case %d:\n",ca++); 139 while(q--) 140 { 141 scanf("%d%d",&a,&b); 142 query(tr,a,b,xx,yy,ans1,ans2); 143 printf("%d %d\n",xx,yy); 144 } 145 } 146 return 0; 147 }
