士兵杀敌（三）简单线段树

  1 #include <vector>
  2 #include <map>
  3 #include <set>
  4 #include <algorithm>
  5 #include <iostream>
  6 #include <cstdio>
  7 #include <cmath>
  8 #include <cstdlib>
  9 #include <string>
 10 #include <cstring>
 11 #include <queue>
 12 using namespace std;
 13 
 14 const int maxn = 100010 , INF = -214748364 , INFF = 0x3f3f3f3f;
 15 int a[maxn], b[4*maxn], c[4*maxn] , A, B;       
 16 
 17 void update(int o, int L, int R)    
 18 {
 19     if(L == R)     
 20         b[o] = B;
 21     else
 22     {
 23         int M = L + (R - L) / 2;
 24         if(A <= M)     
 25             update(2*o, L, M);
 26         else    
 27             update(2*o+1, M+1, R);
 28         b[o] = max(b[2*o], b[2*o+1]);
 29     }
 30 }
 31 
 32 int query(int o, int L, int R)      
 33 {
 34     if(A <= L && R <= B)
 35        return c[o];
 36     int M = L + (R - L) / 2, ans = INF;
 37     if(A <= M)   
 38         ans = max(ans, query(2*o, L, M));
 39     if(B > M)    
 40         ans = max(ans, query(2*o+1, M+1, R));
 41     return ans;
 42 }
 43 
 44 int qquery(int o, int L, int R)      
 45 {
 46     if(A <= L && R <= B)
 47        return b[o];
 48     int M = L + (R - L) / 2, ans = INFF;
 49     if(A <= M)   
 50         ans = min(ans, qquery(2*o, L, M));
 51     if(B > M)    
 52         ans = min(ans, qquery(2*o+1, M+1, R));
 53     return ans;
 54 }
 55 
 56 void build(int o, int L, int R)    
 57 {
 58 
 59     if(L == R)
 60     {
 61         b[o] = a[L];
 62         return;
 63     }
 64     int M = L + (R - L) / 2;
 65     if(L <= M)     
 66         build(2*o, L, M);
 67     if(R > M)      
 68         build(2*o+1, M+1, R);
 69     b[o]=min(b[2*o], b[2*o+1]);
 70 
 71 }
 72 
 73 void build1(int o, int L, int R)    
 74 {
 75 
 76     if(L == R)
 77     {
 78         c[o] = a[L];
 79         return;
 80     }
 81     int M = L + (R - L) / 2;
 82     if(L <= M)     
 83         build1(2*o, L, M);
 84     if(R > M)      
 85         build1(2*o+1, M+1, R);
 86     c[o]=max(c[2*o], c[2*o+1]);
 87 
 88 }
 89 
 90 int main()
 91 {
 92     int N, M;
 93     while(~scanf("%d%d\n", &N, &M))
 94     {
 95         b[0]=INFF;
 96         for(int i = 1; i <= N; i++) scanf("%d", &a[i]);
 97         build(1, 1, N);
 98         build1(1, 1, N);
 99         while(M--)
100         {
101             scanf("%d%d", &A, &B);
102             
103             int minn= qquery(1, 1, N);
104             
105             int maxx= query(1, 1, N);
106             printf("%d\n",maxx-minn);
107         }
108     }
109     return 0;
110 }