79 lines
2.2 KiB
C
79 lines
2.2 KiB
C
/**
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* File: subset_sum_i.c
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* Created Time: 2023-07-29
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* Author: Gonglja (glj0@outlook.com)
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*/
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#include "../utils/common.h"
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#define MAX_SIZE 100
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#define MAX_RES_SIZE 100
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// State (subset)
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int state[MAX_SIZE];
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int stateSize = 0;
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// Result list (subset list)
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int res[MAX_RES_SIZE][MAX_SIZE];
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int resColSizes[MAX_RES_SIZE];
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int resSize = 0;
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/* Backtracking algorithm: Subset Sum I */
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void backtrack(int target, int *choices, int choicesSize, int start) {
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// When the subset sum equals target, record the solution
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if (target == 0) {
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for (int i = 0; i < stateSize; ++i) {
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res[resSize][i] = state[i];
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}
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resColSizes[resSize++] = stateSize;
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return;
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}
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// Traverse all choices
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// Pruning two: start traversing from start to avoid generating duplicate subsets
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for (int i = start; i < choicesSize; i++) {
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// Pruning one: if the subset sum exceeds target, end the loop immediately
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// This is because the array is sorted, and later elements are larger, so the subset sum will definitely exceed target
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if (target - choices[i] < 0) {
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break;
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}
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// Attempt: make a choice, update target, start
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state[stateSize] = choices[i];
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stateSize++;
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// Proceed to the next round of selection
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backtrack(target - choices[i], choices, choicesSize, i);
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// Retract: undo the choice, restore to the previous state
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stateSize--;
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}
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}
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/* Comparison function */
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int cmp(const void *a, const void *b) {
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return (*(int *)a - *(int *)b);
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}
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/* Solve Subset Sum I */
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void subsetSumI(int *nums, int numsSize, int target) {
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qsort(nums, numsSize, sizeof(int), cmp); // Sort nums
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int start = 0; // Start point for traversal
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backtrack(target, nums, numsSize, start);
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}
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/* Driver Code */
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int main() {
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int nums[] = {3, 4, 5};
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int numsSize = sizeof(nums) / sizeof(nums[0]);
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int target = 9;
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subsetSumI(nums, numsSize, target);
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printf("Input array nums =");
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printArray(nums, numsSize);
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printf("target = %d\n", target);
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printf("All subsets equal to %d res = \n", target);
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for (int i = 0; i < resSize; ++i) {
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printArray(res[i], resColSizes[i]);
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}
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return 0;
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}
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