python 基础算法

概述1#算法：解决问题的方法和步骤23#排序算法4#选择排序5defselect(items,comp=lambdax,y:x<y):6#通过隐藏函数lambda判断两个数的大小7items=items[:]8foriinrange(len(items)-1):9min=i10forj

  1 #算法：解决问题的方法和步骤  2   3 #排序算法  4 #选择排序  5 def select(items, comp = lambda x,y : x <y):  6     #通过隐藏函数lambda判断两个数的大小  7     items = items[:]  8     for i in range(len(items) - 1):  9         min = i 10         for j in range(i+1, len(items)): 11             if comp(items[j], items[min]): 12                 #获得j以后的最小值 13                 min = j 14         items[i], items[min] = items[min], items[i] 15         #将判断得到的最小值放在前面 16     return items 17  18 #冒泡排序 19 def maopao(items, tem = lambda x, y : x > y): 20     items = items[:] 21     for i in range(len(items) - 1): 22         exambine = False 23         for j in range(len(items) - 1 - i): 24             #把最大的放在最后 25             if tem(items[j], items[j + 1]): 26                 items[j], items[j + 1] = items[j+1], items[j] 27                 exambine = True 28         if not exambine: 29             break 30     return items 31  32 #搅拌排序 33 def jban_select(items, stm = lambda x, y : x > y): 34     items = items[:] 35     for i in range(len(items)-1): 36         exim = False 37         for j in range(len(items) - 1 -i):  38             #把最大的放到最后 39             if stm(items[j], items[j+1]): 40                 items[j], items[j+1] = items[j+1], items[j] 41                 exim = True 42         if exim: 43             exim = False 44             for x in range(len(items)-2-i, 0, -1): 45                 #把最小的放在最前面 46                 if stm(items[x-1], items[x]): 47                     items[x-1], items[x] = items[x],items[x-1] 48                     exim = True 49         if not exim: 50             break 51     return items 52  53 #归并排序 54 def collect(items1, items2, comp = lambda x,y : x <y): 55     items = [] 56     #print('items1%s' %items1) 57     #print('items2%s' %items2) 58     index1, index2 = 0, 0 59     while index1 < len(items1) and index2 < len(items2): 60         if comp(items1[index1], items2[index2]): 61             items.append(items1[index1]) 62             index1 += 1 63         else: 64             items.append(items2[index2]) 65             index2 += 1 66     items += items1[index1:] 67     items += items2[index2:] 68     #print('items%s'%items) 69     return items 70 def after(items): 71     return sort(List(items)) 72  73 def sort(items): 74     if len(items) < 2: 75         return items 76     mID = len(items) // 2 77     left = sort(items[:mID]) 78     right = sort(items[mID:]) 79     #print('left:%s' %left) 80     #print('right%s' %right) 81     return collect(left, right) 82 print(after([23,45,2,4,5232,1])) 83  84 #查找算法 85 #顺序查找 86 def function(items, key): 87     for number, value in enumerate(items): 88         if value == key: 89             return number 90     return -1 #若不存在key，安全退出 91  92 #折半查找 93 def half_holt(items, key): 94     #items为从小到大排列 95     start, end = 0, len(items)-1 96     while start < end: 97         mID = (start + end) // 2 98         if key < items[mID]: 99             end = mID -1100         elif key > items[mID]:101             start = mID +1102         else:103             return mID104     return -1105 106 #穷举法(百元百鸡)107 #公鸡5元一只，母鸡3元一只，小鸡1元3只108 for i in range(20):109     for j in range(33):110         k = 100 - i - j111         if i*5 + j*3 + k/3 == 100 and k % 3 == 0:112             print('公鸡%d只，母鸡%d只，小鸡%d只' %(i, j, k))113 114 #五人分鱼115 fish = 6116 while True:117     total = fish118     enough = True119     for _ in range(5):120         #保证5次分鱼都是一样的121         if (total-1) % 5 == 0:122             total = (total - 1) // 5 *4123         else:124             enough = False125             break126     if enough:127         print(fish)128         break129     fish += 5130 131 #贪婪法(不追求最优解，快速找到满意解)132 class power_weight():133 134     def __init__(self, name, price, weight):135         self.name = name136         self.weight = weight137         self.price = price138     @property139     def thing_count(self):140         return self.price / self.weight141 142 def ip_thing():143     name, weight, price = input('拥有的物品及属性：').split()144     #split() 通过指定分隔符对字符串进行切片145     return name, int(weight), int(price)146 147 def main():148     max_weight, mun_thing = map(int, input('总重和总的物品件数：').split())149     #map(function, iterable, ...),对序列根据方法排序150     thing_rate = []151     for _ in range(mun_thing):152         thing_rate.append(power_weight(*ip_thing()))153     thing_rate.sort(key=lambda x : x.thing_count ,reverse = True)154     #key=lambda x : x.thing_count 不太懂155     total_weight = 0156     total_price = 0157     print('ok')158     for thing in thing_rate:159         if total_weight + thing.weight <= max_weight:160             print(f'小偷带走了{thing.name}')161             total_weight += thing.weight162             total_price += thing.price163     print(f'总价值{total_price}美元')164 165 if __name__ == '__main__':166         main()167 168 #快速排列(选择枢轴对元素进行划分，左边都比枢轴小右边都比枢轴大)169 def main(items, comp = lambda x, y : x <= y):170     items = items[:]171     func1(items, 0, len(items) - 1, comp)172     return items173 174 def func1(items, start ,end, comp):175     if start < end:176         pol = func2(items, start, end, comp)177         func1(items, start, pol-1, comp)178         func1(items, pol +1, end,comp)179 180 def func2(items, start, end, comp):181     boss = items[end]182     i = start -1183     for j in range(start, end):184         if comp(items[j], boss):185             i +=1186             items[i], items[j] = items[j], items[i]187     items[i+1], items[end] = items[end], items[i+1]188     return i+1189 190 #动态规则191 items = List(map(int, input('输入数列').split()))192 overall = part = items[0]193 for i in range(1, len(items)):194     part = max(items[i], part+items[i])195     overall = max(part, overall)196 print(overall)

 

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