Adding solution for 1854

solutions/1854.java

@@ -0,0 +1,23 @@
+class Solution {
+    public int maximumPopulation(int[][] logs) {
+        int[] year=new int[2051];int max=0;
+        for(int[] i:logs){
+            year[i[0]]+=1;
+            year[i[1]]-=1;
+            if(i[1]>max)
+                max=i[1];
+        }
+        int[] prefix=new int[max+1];
+        for(int i=1950;i<=max;i++){
+            prefix[i]=prefix[i-1]+year[i];
+        }
+        int my=0,m=0;
+        for(int i=1950;i<=max;i++){
+            if(m<prefix[i]){
+                m=prefix[i];
+                my=i;
+            }
+        }
+        return my;
+    }
+}

solutions/1866.java

@@ -0,0 +1,28 @@
+class Solution {
+    public boolean findRotation(int[][] mat, int[][] target) {
+        for(int i=1;i<=4;i++){
+            if(Arrays.deepEquals(mat,target))
+                return true;
+            mat=rotate(mat);
+        }
+        return false;
+    }
+    static int[][] rotate(int[][] m){
+        int temp,n=m.length;
+        int[][] ans=new int[n][n];
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n;j++){
+                ans[i][j]=m[j][i];
+                ans[j][i]=m[i][j];
+            }
+        }
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n/2;j++){
+                temp=ans[i][j];
+                ans[i][j]=ans[i][n-j-1];
+                ans[i][n-j-1]=temp;
+            }
+        }
+        return ans;
+    }
+}