分享代碼--求整數冪以及LeetCode 334

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今天分享如何求整數冪，代碼來自書籍《演算法心得，演算法高效的奧秘》，代碼如下：

#include<stdio.h>int iexp(int x, unsigned n){ int p ,y ; y =1; // Initialize result p =x; // and p. while(1){ if(n&1)y = p*y; // if n is odd, mult by p. n =n>>1; // position next bit of n if(n == 0)return y; // if no bits in n p = p*p; // power for next bit of n }}

LeetCode 334：Increasing Triplet Subsequence

Given an unsorted array return whether an increasing subsequence of length 3 exists(存在) or not in the array.

Formally the function should:

Return true if there exists i, j, k

such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return false.

Your algorithm should run in O(n) time complexity and O(1) space complexity.

Examples:

Given [5, 4, 3, 2, 1],

此題容易誤解，建議多讀幾遍。

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