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| 1 | +#include <iostream> |
| 2 | +#include <vector> |
| 3 | +#include <stack> |
| 4 | +using namespace std; |
| 5 | + |
| 6 | +//左右指针 |
| 7 | +int sort1(vector<int>& v,int left,int right) |
| 8 | +{ |
| 9 | + int key = right; |
| 10 | + while(left < right) |
| 11 | + { |
| 12 | + //无论排升序还是降序都必须是左边先走 |
| 13 | + //也就是说，关键码在右边就左边先走，关键码在左边右边先走 |
| 14 | + //左边先走找大 |
| 15 | + while(left < right && v[left] <= v[key]) |
| 16 | + { |
| 17 | + left++; |
| 18 | + } |
| 19 | + //右边再走找小 |
| 20 | + while(left < right && v[right] >= v[key]) |
| 21 | + { |
| 22 | + right--; |
| 23 | + } |
| 24 | + //左右交换 |
| 25 | + swap(v[left],v[right]); |
| 26 | + } |
| 27 | + //交换 |
| 28 | + swap(v[right],v[key]); |
| 29 | + |
| 30 | + return right; |
| 31 | +} |
| 32 | + |
| 33 | +//前后指针 |
| 34 | +int sort2(vector<int>& v,int left,int right) |
| 35 | +{ |
| 36 | + //当cur小于key时prev++ |
| 37 | + //当cur大于key时，prev不变 |
| 38 | + //cur再次小于key时，cur和prev交换 |
| 39 | + //实际上，也就是让prev始终指向大的的时候就交换 |
| 40 | + |
| 41 | + int cur = left; |
| 42 | + int prev = cur-1; |
| 43 | + |
| 44 | + while(cur <= right) |
| 45 | + { |
| 46 | + if(v[cur] <= v[right] && ++prev != cur) |
| 47 | + { |
| 48 | + swap(v[prev],v[cur]); |
| 49 | + } |
| 50 | + cur++; |
| 51 | + } |
| 52 | + |
| 53 | + return prev; |
| 54 | +} |
| 55 | + |
| 56 | +//挖坑法 |
| 57 | +int sort3(vector<int>& v,int left,int right) |
| 58 | +{ |
| 59 | + int flag = v[right]; |
| 60 | + while(left < right) |
| 61 | + { |
| 62 | + //左边走找比坑的位置大的元素 |
| 63 | + while(left < right && v[left] <= flag) |
| 64 | + { |
| 65 | + left++; |
| 66 | + } |
| 67 | + //将左边的大值填到右边的小坑,左边形成新的坑 |
| 68 | + v[right] = v[left]; |
| 69 | + //右边走找比坑位置小的元素 |
| 70 | + while(left < right && v[right] >= flag) |
| 71 | + { |
| 72 | + right--; |
| 73 | + } |
| 74 | + //将右边的小值填到左边的大坑 |
| 75 | + v[left] = v[right]; |
| 76 | + } |
| 77 | + |
| 78 | + //将flag填到坑位置 |
| 79 | + v[left] = flag; |
| 80 | + |
| 81 | + return left; |
| 82 | +} |
| 83 | + |
| 84 | +//递归实现 |
| 85 | +void QuickSort(vector<int>& v,int left,int right) |
| 86 | +{ |
| 87 | + //左右指针 |
| 88 | + /*if(left >= right) |
| 89 | + return; |
| 90 | + int index = sort1(v,left,right); |
| 91 | + QuickSort(v,left,index-1); |
| 92 | + QuickSort(v,index+1,right);*/ |
| 93 | + |
| 94 | + //前后指针 |
| 95 | + if(left >= right) |
| 96 | + return ; |
| 97 | + |
| 98 | + /*int index = sort2(v,left,right); |
| 99 | + QuickSort(v,left,index-1); |
| 100 | + QuickSort(v,index+1,right);*/ |
| 101 | + |
| 102 | + int index = sort3(v,left,right); |
| 103 | + QuickSort(v,left,index-1); |
| 104 | + QuickSort(v,index+1,right); |
| 105 | +} |
| 106 | + |
| 107 | +//非递归实现 |
| 108 | +void QuickSort1(vector<int>& v) |
| 109 | +{ |
| 110 | + //存储索引的栈 |
| 111 | + stack<pair<int,int>> st; |
| 112 | + //begin和end入栈 |
| 113 | + st.push(make_pair(0,v.size()-1)); |
| 114 | + |
| 115 | + //进行快排 |
| 116 | + while(!st.empty()) |
| 117 | + { |
| 118 | + pair<int,int> p = st.top(); |
| 119 | + st.pop(); |
| 120 | + int index = sort1(v,p.first,p.second); |
| 121 | + //左右部分索引继续入栈 |
| 122 | + if(index - 1 > p.first) |
| 123 | + st.push(make_pair(p.first,index-1)); |
| 124 | + if(index + 1 < p.second) |
| 125 | + st.push(make_pair(index+1,p.second)); |
| 126 | + } |
| 127 | +} |
| 128 | + |
| 129 | +int main() |
| 130 | +{ |
| 131 | + vector<int> v(15); |
| 132 | + v = {1,9,2,4,0,6,8,2,5,3,4,6,8,34,25,8}; |
| 133 | + |
| 134 | + for(auto e:v) |
| 135 | + { |
| 136 | + cout<<e<<" "; |
| 137 | + } |
| 138 | + cout<<endl; |
| 139 | + |
| 140 | + QuickSort(v,0,v.size()-1); |
| 141 | + for(auto e:v) |
| 142 | + { |
| 143 | + cout<<e<<" "; |
| 144 | + } |
| 145 | + cout<<endl; |
| 146 | + v = {1,9,2,4,0,6,8,2,5,3,4,6,8,34,25,8}; |
| 147 | + |
| 148 | + QuickSort1(v); |
| 149 | + for(auto e:v) |
| 150 | + { |
| 151 | + cout<<e<<" "; |
| 152 | + } |
| 153 | + cout<<endl; |
| 154 | + |
| 155 | + return 0; |
| 156 | +} |
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