Commit 0e4fa45

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Improvement

Signed-off-by: begeekmyfriend <begeekmyfriend@gmail.com>

1 parent 15d6c5f commit 0e4fa45Copy full SHA for 0e4fa45

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+17

-8

lines changed

+17

-8

lines changed

Lines changed: 4 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -21,22 +21,22 @@ static void reverse(int *a, int size)`
`21`	`21`
`22`	`22`	`static void nextPermutation(int* nums, int numsSize)`
`23`	`23`	`{`
`24`		`- if (numsSize <= 1) {`
`25`		`- return;`
`26`		`- }`
`27`		`-`
	`24`	`+ // find the first smaller element in decreasing sequence from back to forth.`
`28`	`25`	`int i = numsSize - 2;`
`29`	`26`	`while (i >= 0 && nums[i] >= nums[i + 1]) {`
`30`	`27`	`i--;`
`31`	`28`	`}`
`32`	`29`
	`30`	`+ // if found, find the first bigger element from back to forth and swap them.`
`33`	`31`	`if (i >= 0) {`
`34`	`32`	`int j = numsSize - 1;`
`35`	`33`	`while (j >= 0 && nums[j] <= nums[i]) {`
`36`	`34`	`j--;`
`37`	`35`	`}`
`38`	`36`	`swap(nums + i, nums + j);`
`39`	`37`	`}`
	`38`	`+`
	`39`	`+ // reverse the subsequence into increasing one.`
`40`	`40`	`reverse(nums + i + 1, numsSize - i - 1);`
`41`	`41`	`}`
`42`	`42`

Lines changed: 5 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -5,11 +5,15 @@ using namespace std;`
`5`	`5`	`class Solution {`
`6`	`6`	`public:`
`7`	`7`	`void nextPermutation(vector<int>& nums) {`
	`8`	`+ // find the first smaller element in decreasing sequence from back to`
	`9`	`+ // forth.`
`8`	`10`	`int i = nums.size() - 2;`
`9`	`11`	`while (i >= 0 && nums[i] >= nums[i + 1]) {`
`10`	`12`	`i--;`
`11`	`13`	`}`
`12`	`14`
	`15`	`+ // if found, find the first bigger element from back to forth and swap`
	`16`	`+ // them.`
`13`	`17`	`if (i >= 0) {`
`14`	`18`	`int j = nums.size() - 1;`
`15`	`19`	`while (j >= 0 && nums[i] >= nums[j]) {`
`@@ -18,6 +22,7 @@ class Solution {`
`18`	`22`	`swap(nums[i], nums[j]);`
`19`	`23`	`}`
`20`	`24`
	`25`	`+ // reverse the subsequence into increasing one.`
`21`	`26`	`reverse(nums.begin() + i + 1, nums.end());`
`22`	`27`	`}`
`23`	`28`	`};`

Lines changed: 8 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -26,7 +26,7 @@ static void quick_sort(int *nums, int lo, int hi)`
`26`	`26`	`return;`
`27`	`27`	`}`
`28`	`28`
`29`		`- /* shuffle the pivot */`
	`29`	`+ /* shuffle the pivot as it is a must for performance */`
`30`	`30`	`mid = lo + (hi - lo) / 2;`
`31`	`31`	`swap(&nums[mid], &nums[hi]);`
`32`	`32`
`@@ -38,11 +38,15 @@ static void quick_sort(int *nums, int lo, int hi)`
`38`	`38`	`* shall make the partition in the middle of the array as far as`
`39`	`39`	`* possible. If the partition is located in the head or tail, the`
`40`	`40`	`* performance might well be very bad for it.`
	`41`	`+ *`
	`42`	`+ * Note: Do NOT use nums[++i] <= pivot or nums[--j] >= pivot as the`
	`43`	`+ * loop condition because it leads to redundant operations in each`
	`44`	`+ * recusive iteration when there are many duplicate elements.`
`41`	`45`	`*/`
`42`		`- while (i < hi && nums[++i] < pivot) {}`
`43`		`- while (j>lo && nums[--j] > pivot) {}`
	`46`	`+ while (i < j && nums[++i] < pivot) {}`
	`47`	`+ while (i<j && nums[--j] > pivot) {}`
`44`	`48`	`if (i < j) {`
`45`		`- swap(&nums[i], &nums[j]);`
	`49`	`+ swap(&nums[i], &nums[j]);`
`46`	`50`	`}`
`47`	`51`	`}`
`48`	`52`

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