Usually T questions or ACM time limit is 1 second or 2 seconds.
In this case, the number of operations of the control C ++ code 10 . 7 is the best.
Given below at different data ranges, and how the time complexity of the algorithm selection code:
n≤30, index level, dfs + pruning, state compression dp
n≤100 => O(n3)，floyd，dp
n≤1000 => O (n2logn) (n2) O, dp, bipartite
n≤10000 => O (n * n√), block list
n≤100000 => O (nlogn) => various Sort, segment tree, the tree array, set / map, heap, dijkstra + heap, spfa, seeking convex hull, a half plane cross-seeking, bipartite
n≤1000000 => O (n), and smaller constant O (nlogn) algorithm => hash, two-hand scan, kmp, AC automaton, a relatively small constant O (nlogn) approach: sort, Fenwick tree , heap, Dijkstra, SPFA
n≤10000000 => O (n), dual-scan pointer, kmp, AC automaton, linear sieve primes
n ≤ 10 . 9 => O (n√), a prime number is determined
n ≤ 10 18 => O (logN), the greatest common divisor matrix power quickly met many times need to pay attention