feat: add Longest Square Streak in an Array (#1185)

Co-authored-by: David Leal <halfpacho@gmail.com>

leetcode/DIRECTORY.md

@@ -124,3 +124,4 @@
 | 2256 | [Minimum Average Difference](https://leetcode.com/problems/minimum-average-difference/)                                         | [C](./src/2256.c) | Medium     |
 | 2270 | [Number of Ways to Split Array](https://leetcode.com/problems/number-of-ways-to-split-array/)                                   | [C](./src/2270.c) | Medium     |
 | 2304 | [Minimum Path Cost in a Grid](https://leetcode.com/problems/minimum-path-cost-in-a-grid/)                                       | [C](./src/2304.c) | Medium     |
+| 2501 | [Longest Square Streak in an Array](https://leetcode.com/problems/longest-square-streak-in-an-array/description/)               | [C](./src/2501.c) | Medium     |

leetcode/src/2501.c

@@ -0,0 +1,52 @@
+#define max(a,b) (((a)>(b))?(a):(b))
+
+int longestSquareStreakDp(int* numsSet, int numsSetSize, int* dp, long num){
+    if (dp[num] != 0){
+        return dp[num];
+    }
+
+    long numSquare = num * num;
+
+    dp[num] = 1;
+    if (numSquare <= numsSetSize && numsSet[numSquare] == 1){
+        dp[num] += longestSquareStreakDp(numsSet, numsSetSize, dp, numSquare);
+    }
+
+    return dp[num];
+}
+
+// Dynamic approach. Up -> down.
+// Runtime: O(numsSize)
+// Space: O(max(nums))
+int longestSquareStreak(int* nums, int numsSize){
+    // Find nums maximum
+    int numMax = 0;
+    for(int i = 0; i < numsSize; i++){
+        numMax = max(numMax, nums[i]);
+    }
+
+    int* numsSet = calloc(numMax + 1, sizeof(int));
+    int* dp = calloc(numMax + 1, sizeof(int));
+    
+    // Init set of nums
+    for(int i = 0; i < numsSize; i++){
+        numsSet[nums[i]] = 1;
+    }
+
+    // Find result
+    int result = -1;
+    for(int i = 0; i < numsSize; i++){
+        long num = nums[i];
+        long numSquare = num * num;
+
+        if (numSquare > numMax || numsSet[numSquare] == 0){
+            continue;
+        }
+
+        result = max(result, 1 + longestSquareStreakDp(numsSet, numMax, dp, numSquare));
+    }
+
+    free(dp);
+    free(numsSet);
+    return result;
+}