uva 11991 Easy Problem from Rujia Liu

原题链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=18696 
方法很多，我用的是快排+二分，练习一下stl lower_bound这个函数。。。

 1 #include<algorithm>

 2 #include<iostream>

 3 #include<cstdlib>

 4 #include<cstring>

 5 #include<cstdio>

 6 using std::sort;

 7 using std::lower_bound;

 8 const int Max_N = 100010;

 9 struct node {

10     int v, id;

11 }rec[Max_N];

12 int arr[Max_N];

13 bool cmp(node &a, node &b) {

14     if (a.v == b.v) return a.id < b.id;

15     return a.v < b.v;

16 }

17 int main() {

18 #ifdef LOCAL

19     freopen("in.txt", "r", stdin);

20     freopen("out.txt", "w+", stdout);

21 #endif

22     int n, m, a, b, pos;

23     while (~scanf("%d %d", &n, &m)) {

24         for (int i = 0; i < n; i++) {

25             scanf("%d", &rec[i].v);

26             rec[i].id = i + 1;

27         }

28         sort(rec, rec + n, cmp);

29         for (int i = 0; i < n; i++) arr[i] = rec[i].v;

30         while (m--) {

31             scanf("%d %d", &a, &b);

32             pos = lower_bound(arr, arr + n, b) - arr;

33             node &k = rec[pos + a - 1];

34             if (k.v == b) printf("%d\n", k.id);

35             else puts("0");

36         }

37     }

38     return 0;

39 }

View Code