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45 lines
1001 B
45 lines
1001 B
package class41;
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public class Problem_0031_NextPermutation {
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public static void nextPermutation(int[] nums) {
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int N = nums.length;
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// 从右往左第一次降序的位置
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int firstLess = -1;
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for (int i = N - 2; i >= 0; i--) {
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if (nums[i] < nums[i + 1]) {
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firstLess = i;
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break;
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}
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}
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if (firstLess < 0) {
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reverse(nums, 0, N - 1);
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} else {
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int rightClosestMore = -1;
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// 找最靠右的、同时比nums[firstLess]大的数，位置在哪
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// 这里其实也可以用二分优化，但是这种优化无关紧要了
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for (int i = N - 1; i > firstLess; i--) {
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if (nums[i] > nums[firstLess]) {
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rightClosestMore = i;
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break;
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}
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}
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swap(nums, firstLess, rightClosestMore);
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reverse(nums, firstLess + 1, N - 1);
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}
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}
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public static void reverse(int[] nums, int L, int R) {
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while (L < R) {
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swap(nums, L++, R--);
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}
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}
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public static void swap(int[] nums, int i, int j) {
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int tmp = nums[i];
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nums[i] = nums[j];
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nums[j] = tmp;
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}
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}
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