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Commit 7c2d3db

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Signed-off-by: begeekmyfriend <begeekmyfriend@gmail.com>
1 parent 3c3d486 commit 7c2d3db

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7 files changed

+55
-41
lines changed

7 files changed

+55
-41
lines changed

‎039_combination_sum/combination_sum.c‎

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6,14 +6,17 @@ static void dfs(int *nums, int size, int start, int target, int *stack,
66
int len, int **results, int *count, int *column_sizes)
77
{
88
int i;
9-
if (target == 0) {
9+
if (target < 0) {
10+
return;
11+
} else if (target == 0) {
1012
results[*count] = malloc(len * sizeof(int));
1113
memcpy(results[*count], stack, len * sizeof(int));
1214
column_sizes[*count] = len;
1315
(*count)++;
14-
} else if (target>0) {
16+
} else {
1517
for (i = start; i < size; i++) {
1618
stack[len] = nums[i];
19+
/* The elements in solution can be duplicate for the purpose of the problem */
1720
dfs(nums, size, i, target - nums[i], stack, len + 1, results, column_sizes, count);
1821
}
1922
}

‎040_combination_sum_ii/combination_sum.c‎

Lines changed: 13 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -8,29 +8,27 @@ static int compare(const void *a, const void *b)
88
return *(int *) a - *(int *) b;
99
}
1010

11-
static void dfs(int *nums, int size, int start, int target, int *solution,intlen,
12-
bool*used, int **results, int *count, int *column_sizes)
11+
static void dfs(int *nums, int size, int start, int target, int *solution,
12+
intlen, int **results, int *count, int *column_sizes)
1313
{
1414
int i;
15-
if (target == 0) {
15+
if (target < 0) {
16+
return;
17+
} else if (target == 0) {
1618
results[*count] = malloc(len * sizeof(int));
1719
memcpy(results[*count], solution, len * sizeof(int));
1820
column_sizes[*count] = len;
1921
(*count)++;
20-
} else if (target > 0) {
22+
} else {
23+
int last = -1;
2124
for (i = start; i < size; i++) {
22-
if (!used[i]) {
23-
if (i > 0 && !used[i - 1] && nums[i - 1] == nums[i]) {
24-
/* Forbid same elements in same level */
25-
/* Used marks allow same elements in different levels */
26-
continue;
27-
}
28-
used[i] = true;
25+
if (last != nums[i]) {
26+
/* No duplicate combinations in different order */
2927
solution[len] = nums[i];
30-
/* i + 1 limits the selecting range in following levels */
31-
dfs(nums, size, i + 1, target - nums[i], solution, len + 1, used, results, count, column_sizes);
32-
used[i] = false;
28+
/* i + 1 limits the candidate range in next levels */
29+
dfs(nums, size, i + 1, target - nums[i], solution, len + 1, results, count, column_sizes);
3330
}
31+
last = nums[i];
3432
}
3533
}
3634
}
@@ -46,11 +44,9 @@ static int** combinationSum(int* candidates, int candidatesSize, int target, int
4644

4745
int *solution = malloc(target * sizeof(int));
4846
int **results = malloc(100 * sizeof(int *));
49-
bool *used = malloc(candidatesSize);
50-
memset(used, false, candidatesSize);
5147
*returnColumnSizes = malloc(100 * sizeof(int));
5248
*returnSize = 0;
53-
dfs(candidates, candidatesSize, 0, target, solution, 0, used, results, returnSize, *returnColumnSizes);
49+
dfs(candidates, candidatesSize, 0, target, solution, 0, results, returnSize, *returnColumnSizes);
5450
return results;
5551
}
5652

‎046_permutations/permutations.c‎

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3,13 +3,35 @@
33
#include <stdbool.h>
44
#include <string.h>
55

6+
#if 0
67
static void swap(int *a, int *b)
78
{
89
int tmp = *a;
910
*a = *b;
1011
*b = tmp;
1112
}
1213

14+
static void dfs(int *nums, int size, int start,
15+
int **results, int *count, int *col_size)
16+
{
17+
int i;
18+
if (start == size) {
19+
results[*count] = malloc(size * sizeof(int));
20+
memcpy(results[*count], nums, size * sizeof(int));
21+
col_size[*count] = size;
22+
(*count)++;
23+
} else {
24+
for (i = start; i < size; i++) {
25+
/* A swap can make a new permutation but not be listed in order */
26+
swap(nums + start, nums + i);
27+
dfs(nums, size, start + 1, results, count, col_size);
28+
/* restore the array in backtrace */
29+
swap(nums + start, nums + i);
30+
}
31+
}
32+
}
33+
#endif
34+
1335
static void dfs(int *nums, int size, bool *used, int *stack,
1436
int len, int **results, int *count, int *col_size)
1537
{
@@ -22,6 +44,7 @@ static void dfs(int *nums, int size, bool *used, int *stack,
2244
} else {
2345
for (i = 0; i < size; i++) {
2446
if (!used[i]) {
47+
/* */
2548
used[i] = true;
2649
stack[len] = nums[i];
2750
dfs(nums, size, used, stack, len + 1, results, count, col_size);

‎047_permutations_ii/permutations.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -21,8 +21,8 @@ static void dfs(int *nums, int size, bool *used, int *stack,
2121
for (i = 0; i < size; i++) {
2222
if (!used[i]) {
2323
if (i > 0 && nums[i] == nums[i - 1] && !used[i - 1]) {
24-
/* Forbid same elements on same level */
25-
/* Used marks allow same elements in different levels */
24+
/* In case that duplicate permutation with same elemements */
25+
/* Used marks allow same elements in different DFS levels */
2626
continue;
2727
}
2828
used[i] = true;

‎051_n_queens/n_queens.c‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -65,7 +65,6 @@ static void dfs(int n, int row, int *stack, char ***solutions, int *count, int *
6565
if (row == 0 || !conflict(stack, row, col)) {
6666
stack[row] = col;
6767
dfs(n, row + 1, stack, solutions, count, col_sizes);
68-
continue;
6968
}
7069
}
7170
}

‎077_combinations/combinations.c‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,6 @@ static void dfs(int n, int k, int start, int *stack, int len,
1414
(*count)++;
1515
} else {
1616
for (i = start; i <= n; i++) {
17-
/* No used marks since the order does not matter */
1817
stack[len] = i;
1918
dfs(n, k, i + 1, stack, len + 1, results, count, col_sizes);
2019
}

‎090_subsets_ii/subsets.c‎

Lines changed: 12 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,4 @@
1+
#include <limits.h>
12
#include <stdio.h>
23
#include <stdlib.h>
34
#include <stdbool.h>
@@ -8,46 +9,39 @@ static inline int compare(const void *a, const void *b)
89
return *(int *) a - *(int *) b;
910
}
1011

11-
static void dfs(int *nums, int size, int start, int *buf,intlevel,
12-
bool*used, int **sets, int *count, int *sizes)
12+
static void dfs(int *nums, int size, int start, int *buf,
13+
intlevel, int **sets, int *count, int *sizes)
1314
{
14-
int i;
15+
int i, last=INT_MIN;
1516
sets[*count] = malloc(level * sizeof(int));
1617
memcpy(sets[*count], buf, level * sizeof(int));
1718
sizes[*count] = level;
1819
(*count)++;
1920
for (i = start; i < size; i++) {
20-
if (!used[i]) {
21-
if (i > 0 && !used[i - 1] && nums[i - 1] == nums[i]) {
22-
/* Forbid same elements on same level */
23-
/* Used marks allow same elements in different levels */
24-
continue;
25-
}
26-
used[i] = true;
21+
if (last != nums[i]) {
22+
/* No duplicate candidate elements at same level position */
2723
buf[level] = nums[i];
28-
/* i + 1 limits the selecting range in following levels */
29-
dfs(nums, size, i + 1, buf, level + 1, used, sets, count, sizes);
30-
used[i] = false;
24+
/* i + 1 limits the selecting range in next levels */
25+
dfs(nums, size, i + 1, buf, level + 1, sets, count, sizes);
3126
}
27+
last = nums[i];
3228
}
3329
}
3430

3531
/**
3632
** Return an array of arrays of size *returnSize.
3733
** The sizes of the arrays are returned as *returnColumnSizes array.
38-
** Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
34+
** Note: Both returned array and *returnColumnSizes array must be malloced, assume caller calls free().
3935
**/
40-
static int** subsets(int* nums, int numsSize, int* returnSize, int** returnColumnSizes)
36+
static int** subsetsWithNoDup(int* nums, int numsSize, int* returnSize, int** returnColumnSizes)
4137
{
4238
qsort(nums, numsSize, sizeof(int), compare);
4339
int capacity = 5000;
4440
int **sets = malloc(capacity * sizeof(int *));
4541
int *buf = malloc(numsSize * sizeof(int));
46-
bool *used = malloc(numsSize);
47-
memset(used, false, numsSize);
4842
*returnColumnSizes = malloc(capacity * sizeof(int));
4943
*returnSize = 0;
50-
dfs(nums, numsSize, 0, buf, 0, used, sets, returnSize, *returnColumnSizes);
44+
dfs(nums, numsSize, 0, buf, 0, sets, returnSize, *returnColumnSizes);
5145
return sets;
5246
}
5347

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