Create lexicographicPermutations.c

Program to print all possible Permutations of a string in Lexicographical order.

misc/lexicographicPermutations.c

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+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+void swap(char* left, char* right){
+    char temp = *left;
+    *left = *right;
+    *right = temp;
+}
+
+int compare (const void * a, const void * b){
+    return ( *(char*)a - *(char*)b );
+}
+
+void PrintSortedPermutations(char str[])
+{
+    int strSize = strlen(str);
+    qsort(str, strSize, sizeof(char), compare);
+
+    int largerPermFound = 1;
+    do{
+        // 1. Print permutation
+        printf("%s\n", str);
+        // 2. Find rightmost char that is smaller than char to its right
+        int i;
+        for (i = strSize - 2; i >= 0 && str[i] >= str[i+1]; --i){}
+
+        // if we couldn't find one, we're finished, else we can swap
+        if (i >= 0){
+            // 3. find character at index j such that str[j] = min(str[k]) && str[k] > str[i] for all k > i
+            int j = i+1, k;
+            for(k=j; k<strSize && str[k]; k++){
+                if (str[k] > str[i] && str[k] < str[j])
+                    j = k;
+            }
+            // 3. Swap chars at i and j
+            swap(&str[i], &str[j]);
+            // 4. Sort string to the right of i
+            qsort(str+i+1, strSize-i-1, sizeof(char), compare);
+        }
+        else    largerPermFound = 0;
+    }
+    while(largerPermFound);
+}
+
+int main() {
+    int n; //size of string
+    scanf("%d\n",&n);
+    char str[n];
+    scanf("%s",str);
+    PrintSortedPermutations(str);
+    return 0;
+}