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算法学习

3、

package main
 
import (
    "fmt"
)
 
func max(x int, y int) int {
    if x < y {
        return y
    }
    return x
}
// 窗口滑动 解决子串问题
// 获取最长非重复子串   示例： "acdfeabac" > "acdfe"
func getLongestNotRepeat(s string) int {
    l := 0
    r := 0
    slen := len(s)
 
    currentLen := 1
    currentShou := s[l]
    for ;r<slen;r++ {
        if l >= r  {
            continue
        }else if currentShou == s[r] {
            fmt.Println(s[l:r])
            currentLen = max(currentLen, r-l)
            l++
        }
    }
    return currentLen
}
 
 
func climbStairs(n int) int {
    result := 0
    if n <= 0 {
        return 0
    }
    for _,step := range []int{1,2} {
        if n-step == 0 {
            result++
        } else if n-step >0 {
            result = result + climbStairs(n-step)
        } else if n-step <0 {
            continue
        }
    }
    return result
}
 
type ListNode struct {
    data int
    Next *ListNode
}
 
 
 
 
func main() {
    a := getLongestNotRepeat("acdfeabac")
    fmt.Println(a)
 
    fmt.Println(climbStairs(10))
}

2、读取大文件（5G/10G/1T）

for line in fp.readlines(): #如果line很长时，不合适

for a in fp.read(block_size): # 按块读取

1. threading.Semaphore(value=1) 线程信号量，可以用来控制线程线程的阻塞和释放

sm.acquire() 获取一个信号量，信号量-1，不够-1，则线程阻塞

sm.release() 释放一个信号量，信号量+1

示例如下，控制三个线程的执行顺序：

# -*- coding: utf-8 -*-
import threading
import time
 
sm0 = threading.Semaphore()
sm1 = threading.Semaphore(0)
sm2 = threading.Semaphore(0)
 
a = 0
 
 
def print1():
    global a
    while True:
        sm1.acquire()
        if a % 2 == 1:
            print(a, "----", a, threading.currentThread().name)
            a = a + 1
            time.sleep(1)
        sm0.release()
 
 
def print2():
    global a
    while True:
        sm2.acquire()
        if a % 2 == 0:
            print(a, "----", a, threading.currentThread().name)
            a = a + 1
            time.sleep(1)
        sm0.release()
 
 
def print0():
    global a
    while True:
        sm0.acquire()
        print(0, "----", a)
        time.sleep(1)
        if a % 2 == 1:
            sm1.release()
        else:
            sm2.release()
 
 
if __name__ == '__main__':
    t1 = threading.Thread(target=print1)
    t0 = threading.Thread(target=print0)
    t2 = threading.Thread(target=print2)
    t0.start()
    t1.start()
    t2.start()