【POJ】Buy Tickets（线段树）

点更新用法很巧妙的一道题。倒序很容易的找到该人的位置，而update操作中需要不断的变化下标才能合理的插入。看了别人写的代码，学习了。

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <map>
 using namespace std;
 
 const int maxn = 2e5 + ;
 int sumv[maxn << ], data[maxn];
 
 void PushUp (int rt) {
     sumv[rt] = sumv[rt << ] + sumv[rt <<  | ];
 }
 
 void build (int l, int r, int rt) {
     if (l == r) {
         sumv[rt] = ;
         return ;
     }
     int m = (l + r) / ;
     build (l, m, rt << );
     build (m + , r, rt <<  | );
     PushUp (rt);
 }
 
 void update (int p, int v, int l, int r, int rt) {
     if (l == r) {
         data[l] = v; sumv[rt] = ;
         return ;
     }
     int m = (l + r) >> ;
     if (sumv[rt * ] >= p) {
         update (p, v, l, m, rt * );
     } else {
         update (p - sumv[rt * ], v, m + , r, rt *  + );
     }
     PushUp(rt);
 }
 
 int main () {
     pair<int, int> p[maxn];
     int n;
     while (~scanf ("%d", &n)) {
         for (int i = ; i < n; ++ i) {
             scanf ("%d%d", &p[i].first, &p[i].second);
         }
         build (, n, );
         for (int i = n - ; i >= ; -- i) {
             update (p[i].first + , p[i].second, , n, );
         }
         for (int i = ; i <= n; ++ i) {
             if (i == ) {
                 printf ("%d", data[i]);
             } else {
                 printf (" %d", data[i]);
             }
         }
         puts("");
     }
     return ;
 }