LeetCode 31.Next Permutation
2015-03-17 15:14
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题目:
Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.
If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).
The replacement must be in-place, do not allocate extra memory.
Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.
分析解答:
Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.
If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).
The replacement must be in-place, do not allocate extra memory.
Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.
1,2,3→
1,3,2
3,2,1→
1,2,3
1,1,5→
1,5,1
分析解答:
class Solution { public: void nextPermutation(vector<int> &num) { vector<int>::size_type n = num.size(); if(n==0 || n==1){ return; } int swap_in = 0,swap_out = 0; size_t i = n - 1 , j = 0; for(i = n - 1; i != 0;--i){ if(num[i-1] < num[i]){ swap_in = i - 1; break; } } if(i != 0){ for(i = n - 1; i != swap_in;--i){ if(num[i] > num[swap_in]){ swap_out = i; break; } } vector_swap(num,swap_in,swap_out); j = swap_in + 1; }else{ j = 0; } i = n - 1; while(j < i){ vector_swap(num,j,i); ++j; --i; } } void vector_swap(vector<int> &v,int m,int n){ int temp = v[m]; v[m] = v ; v = temp; } };
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