线段树，最大值查询位子(个人模版)

Posted 2020-09-05 Angel_Kitty

线段树，最大值查询位子：

  1 #include<cstdio>
  2 #include<climits>
  3 #include<algorithm>
  4 
  5 using namespace std;
  6 
  7 #define lson l, m, rt<<1
  8 #define rson m+1, r, (rt<<1)|1
  9 
 10 int tree[111111<<2];
 11 int posn[111111<<2];
 12 void pushup(int rt)
 13 {
 14     if (tree[rt<<1] > tree[rt<<1|1])
 15     {
 16         tree[rt] = tree[rt<<1];
 17         posn[rt] = posn[rt<<1];
 18     }
 19     else
 20     {
 21         tree[rt] = tree[rt<<1|1];
 22         posn[rt] = posn[rt<<1|1];
 23     }
 24 }
 25 void build(int l, int r, int rt)
 26 {
 27     if (l == r)
 28     {
 29         scanf("%d", &tree[rt]);
 30         posn[rt] = l;
 31     }
 32     else
 33     {
 34         int m = (l + r) >> 1;
 35         build(lson);
 36         build(rson);
 37         pushup(rt);
 38     }
 39 }
 40 void update(int p, int val, int l, int r, int rt)
 41 {
 42     if (l == r)
 43     {
 44         tree[rt] = val;
 45     }
 46     else
 47     {
 48         int m = (l + r) >> 1;
 49         if (p <= m)
 50         {
 51             update(p, val, lson);
 52         }
 53         else
 54         {
 55             update(p, val, rson);
 56         }
 57         pushup(rt);
 58     }
 59 }
 60 int query(int L, int R, int l, int r, int rt, int *pos)
 61 {
 62     if (L <= l && r <= R)
 63     {
 64         *pos = posn[rt];
 65         return tree[rt];
 66     }
 67     else
 68     {
 69         int m = (l + r) >> 1;
 70         int ret1 = INT_MIN;
 71         int ret2 = INT_MIN;
 72         int pa, pb;
 73         int *pos1 = &pa;
 74         int *pos2 = &pb;
 75         if (L <= m)
 76         {
 77             ret1 = query(L, R,  lson, pos1);
 78         }
 79         if (R > m)
 80         {
 81             ret2 = query(L, R, rson, pos2);
 82         }
 83         if (ret1 > ret2)
 84         {
 85             *pos = pa;
 86         }
 87         else
 88         {
 89             *pos = pb;
 90             ret1 = ret2;
 91         }
 92         return ret1;
 93     }
 94 }
 95 int main(void)
 96 {
 97     int n, m;
 98 
 99     while (scanf("%d", &n) != EOF)
100     {
101         build(1, n, 1);
102 
103         scanf("%d", &m);
104         char op[2];
105         int a, b;
106         while (m--)
107         {
108             scanf("%s", op);
109             if (op[0] == ‘Q‘)
110             {
111                 int pos;
112                 printf("%d %d\n", pos, query(1, n, 1, n, 1, &pos));
113             }
114             else
115             {
116                 scanf("%d%d", &a, &b);
117                 update(a, b, 1, n, 1);
118             }
119         }
120         printf("\n");
121     }
122 
123     return 0;
124 }