Create Number of Same-End Substrings.java

varunu28 · web-flow · commit 1c1f3cf1277b · 2024-11-06T07:25:20.000-08:00
diff --git a/Medium/Number of Same-End Substrings.java b/Medium/Number of Same-End Substrings.java
@@ -0,0 +1,28 @@
+class Solution {
+    public int[] sameEndSubstringCount(String s, int[][] queries) {
+        int n = s.length();
+        int[][] prefixSum = new int[26][n];
+        for (int i = 0; i < n; i++) {
+            prefixSum[s.charAt(i) - 'a'][i]++;
+        }
+        for (int i = 0; i < 26; i++) {
+            for (int j = 1; j < n; j++) {
+                prefixSum[i][j] += prefixSum[i][j - 1];
+            }
+        }
+        int[] result = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int left = queries[i][0];
+            int right = queries[i][1];
+            int count = 0;
+            for (int c = 0; c < 26; c++) {
+                int leftFreq = left == 0 ? 0 : prefixSum[c][left - 1];
+                int rightFreq = prefixSum[c][right];
+                int freqInRange = rightFreq - leftFreq;
+                count += (freqInRange * (freqInRange + 1)) / 2;
+            }
+            result[i] = count;
+        }
+        return result;
+    }
+}
