Distinct subsequences

Signed-off-by: begeekmyfriend <[email protected]>

115_distinct_subsequences/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test distinct_subseq.c

115_distinct_subsequences/distinct_subseq.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int numDistinct(char* s, char* t)
+{
+    int s_len = strlen(s);
+    int t_len = strlen(t);
+    if (t_len == 0 || s_len < t_len) {
+        return 0;
+    }
+
+    int start = 0;
+    while (start < s_len && s[start] != t[0]) {
+        start++;
+    }
+    if (start == s_len) {
+        return 0;
+    }
+
+    int i, j;
+    int *table = malloc((s_len - start) * t_len * sizeof(int));
+    int **dp = malloc((s_len - start) * sizeof(int *));
+    for (i = 0; i < s_len - start; i++) {
+        dp[i] = &table[i * t_len];
+    }
+
+    dp[0][0] = 1;
+    for (i = 1; i < t_len; i++) {
+        dp[0][i] = 0;
+    }
+
+    for (i = 1; i < s_len - start; i++) {
+        dp[i][0] = dp[i - 1][0];
+        if (s[start + i] == t[0]) {
+            dp[i][0]++;
+        }
+    }
+
+    for (i = 1; i < s_len - start; i++) {
+        for (j = 1; j < t_len; j++) {
+            dp[i][j] = dp[i - 1][j];
+            if (s[start + i] == t[j]) {
+                dp[i][j] += dp[i - 1][j - 1]; 
+            }
+        }
+    }
+
+    return dp[s_len - start - 1][t_len - 1];
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: ./test string pattern\n");
+        exit(-1);
+    }
+    printf("%d\n", numDistinct(argv[1], argv[2]));
+    return 0;
+}