DP | new question added

Author: arorarahul

Diff for: dynamic-programming/question11.c

@@ -73,3 +73,4 @@ int main(){
 	return 0;
 }
 
+

Diff for: dynamic-programming/question35.c

@@ -0,0 +1,75 @@
+/*
+Finding the maximum square sub-matrix with all equal elements
+
+This is similar to finding the largest square sub matrix with all 1s. The only difference here is
+that the numbers can be any. So basically in this case we maintain another matrix initiazed as zero.
+Then if there is a match between all the four elements, considering the right bottom most element
+to be the reference, we increment the count in the ref matrix at the place as min(i,j) + 1
+everytime. 
+
+Time and space complexity is same as that of prev matrix question with all 1's
+
+O(n^2) each
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <string.h>
+
+int findMin(int a, int b){
+	return a < b? a: b;
+}
+
+void initRef(int rows, int cols, int ref[rows][cols]){
+	int i,j;
+	for(i=0;i<rows;i++){
+		for(j=0;j<cols;j++){
+			ref[i][j] = 0;
+		}
+	}
+}
+
+void findLargestMatrix(int rows, int cols, int arr[rows][cols]){
+	
+	int i, j, max = 0;	
+	int a,b,c;
+	int ref[rows][cols];
+
+	initRef(rows, cols, ref);
+
+	for(i=1;i<rows;i++){
+		for(j=1;j<cols;j++){	
+			a = arr[i-1][j-1];
+			b = arr[i-1][j];
+			c = arr[i][j-1];
+			if(a == b && b == c && c == arr[i][j]){
+				ref[i][j] = findMin(i,j) + 1;
+				if(max < ref[i][j]){
+					max = ref[i][j];
+				}
+			}
+		}
+	}
+
+	printf("%d\n", max);
+}
+
+int main(){
+	
+	int arr[4][4] = {
+		{9,9,9,9},
+		{9,9,9,9},
+		{9,9,9,9},
+		{9,9,9,9}
+	};
+
+	int rows = sizeof(arr)/sizeof(arr[0]);
+
+	int cols = sizeof(arr[0])/sizeof(arr[0][0]);
+
+	findLargestMatrix(rows, cols, arr);
+
+	return 0;
+}

Diff for: test1.c

@@ -1,70 +1,60 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <limits.h>
+#include <string.h>
 
-void maxProductSubArray(int *arr, int size){
-	int i;
-	int countNegatives = 0;
-	for(i=0;i<size;i++){
-		if(arr[i] < 0){
-			countNegatives++;
-		}
-	}
-	int lastCountNegativesValues = countNegatives;
-
-	int curr = 1, max = INT_MIN;
-
-	for(i=0;i<size;i++){
-		curr = curr*arr[i];
-
-		if(curr > max){
-			max = curr;
-		}
-
-		if(arr[i] < 0){
-			countNegatives--;
-		}
+int findMin(int a, int b){
+	return a < b? a: b;
+}
 
-		if((curr < 0 && countNegatives <= 0) || (curr == 0)){
-			curr = 1;
+void initRef(int rows, int cols, int ref[rows][cols]){
+	int i,j;
+	for(i=0;i<rows;i++){
+		for(j=0;j<cols;j++){
+			ref[i][j] = 0;
 		}
 	}
-
-	curr = 1;
-	countNegatives = lastCountNegativesValues;
-
-	for(i=size-1;i>=0;i--){
-		curr = curr*arr[i];
-		if(curr > max){
-			max = curr;
-		}
-
-		if(arr[i] < 0){
-			countNegatives--;
-		}
-
-		if((curr < 0 && countNegatives <= 0) || (curr == 0)){
-			curr = 1;
+}
+
+void findLargestMatrix(int rows, int cols, int arr[rows][cols]){
+	
+	int i, j, max = 0;	
+	int a,b,c;
+	int ref[rows][cols];
+
+	initRef(rows, cols, ref);
+
+	for(i=1;i<rows;i++){
+		for(j=1;j<cols;j++){	
+			a = arr[i-1][j-1];
+			b = arr[i-1][j];
+			c = arr[i][j-1];
+			if(a == b && b == c && c == arr[i][j]){
+				ref[i][j] = findMin(i,j) + 1;
+				if(max < ref[i][j]){
+					max = ref[i][j];
+				}
+			}
 		}
 	}
 
 	printf("%d\n", max);
-}	
+}
 
 int main(){
-	int cases;
-	scanf("%d",&cases);
-	int i;
-	for(i=0;i<cases;i++){
-		int size;
-		scanf("%d",&size);
-		int j;
-		int arr[size];
-		for(j=0;j<size;j++){
-			scanf("%d",&arr[j]);
-		}
-		maxProductSubArray(arr, size);
+	
+	int arr[4][4] = {
+		{9,9,9,9},
+		{9,9,9,9},
+		{9,9,9,9},
+		{9,9,9,9}
+	};
+
+	int rows = sizeof(arr)/sizeof(arr[0]);
+
+	int cols = sizeof(arr[0])/sizeof(arr[0][0]);
+
+	findLargestMatrix(rows, cols, arr);
 
-	}
 	return 0;
 }