Merge pull request chipbk10#117 from chipbk10/Intervals

Intervals

Author: chipbk10

src/contest/ReadMe.java

@@ -23,7 +23,7 @@ public class ReadMe {
     // bit manipulation:    1356[v]     1342[v]     1318[v]     1310[v]     371[v]
     // other:               913[x]      1288[v]     843[x!]     1032[v]     850[x]
 
-    // intervals: 546, 312, 1000, 1353, 1288, 1235, 252, 253, 495, 616, 759, 646, 435       [x]
+    // intervals: 546, 312, 1000, 1353, 1288, 1235, 252, 253, 495, 616, 759, 646, 435, 56       [x]
 
 
     // ~: vague

src/intervals/Problem312_BurstBalloons.java

@@ -0,0 +1,21 @@
+package intervals;
+
+public class Problem312_BurstBalloons {
+
+    public int maxCoins(int[] A) {
+        int n = A.length, dp[][] = new int[n][n];
+        return dfs(A, dp, 0, n-1);
+    }
+
+    private int dfs(int[] A, int[][] dp, int l, int r) {
+        if (l > r) return 0;
+        if (dp[l][r] != 0) return dp[l][r];
+        for (int i = l; i <= r; i++) {
+            int p = A[i];
+            if (l > 0) p *= A[l-1];
+            if (r < A.length-1) p *= A[r+1];
+            dp[l][r] = Math.max(dp[l][r], p + dfs(A, dp, l, i-1) + dfs(A, dp, i+1, r));
+        }
+        return dp[l][r];
+    }
+}

src/intervals/Problem452_MinimumNumberOfArrowsToBurstBalloons.java

@@ -0,0 +1,19 @@
+package intervals;
+
+import java.util.Arrays;
+
+public class Problem452_MinimumNumberOfArrowsToBurstBalloons {
+
+    public int findMinArrowShots(int[][] A) {
+        Arrays.sort(A, (a, b) -> a[1]-b[1]);
+        long burst = Long.MIN_VALUE;
+        int res = 0;
+        for (int[] a : A) {
+            if (burst < a[0]) {
+                burst = (long)a[1];
+                res++;
+            }
+        }
+        return res;
+    }
+}