82 lines
2.4 KiB
C
82 lines
2.4 KiB
C
/**
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* File: permutations_ii.c
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* Created Time: 2023-10-17
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.h"
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// Assume a maximum of 1000 permutations, maximum element size 1000
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#define MAX_SIZE 1000
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/* Backtracking algorithm: Permutation II */
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void backtrack(int *state, int stateSize, int *choices, int choicesSize, bool *selected, int **res, int *resSize) {
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// When the state length equals the number of elements, record the solution
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if (stateSize == choicesSize) {
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res[*resSize] = (int *)malloc(choicesSize * sizeof(int));
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for (int i = 0; i < choicesSize; i++) {
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res[*resSize][i] = state[i];
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}
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(*resSize)++;
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return;
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}
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// Traverse all choices
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bool duplicated[MAX_SIZE] = {false};
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for (int i = 0; i < choicesSize; i++) {
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int choice = choices[i];
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// Pruning: do not allow repeated selection of elements and do not allow repeated selection of equal elements
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if (!selected[i] && !duplicated[choice]) {
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// Attempt: make a choice, update the state
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duplicated[choice] = true; // Record selected element values
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selected[i] = true;
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state[stateSize] = choice;
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// Proceed to the next round of selection
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backtrack(state, stateSize + 1, choices, choicesSize, selected, res, resSize);
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// Retract: undo the choice, restore to the previous state
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selected[i] = false;
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}
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}
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}
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/* Permutation II */
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int **permutationsII(int *nums, int numsSize, int *returnSize) {
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int *state = (int *)malloc(numsSize * sizeof(int));
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bool *selected = (bool *)malloc(numsSize * sizeof(bool));
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for (int i = 0; i < numsSize; i++) {
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selected[i] = false;
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}
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int **res = (int **)malloc(MAX_SIZE * sizeof(int *));
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*returnSize = 0;
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backtrack(state, 0, nums, numsSize, selected, res, returnSize);
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free(state);
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free(selected);
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return res;
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}
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/* Driver Code */
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int main() {
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int nums[] = {1, 1, 2};
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int numsSize = sizeof(nums) / sizeof(nums[0]);
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int returnSize;
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int **res = permutationsII(nums, numsSize, &returnSize);
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printf("Input array nums =");
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printArray(nums, numsSize);
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printf("\nAll permutations res = \n");
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for (int i = 0; i < returnSize; i++) {
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printArray(res[i], numsSize);
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}
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// Free memory
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for (int i = 0; i < returnSize; i++) {
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free(res[i]);
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}
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free(res);
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return 0;
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}
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