Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.
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package com.omt.learn.algo; public class RainWaterTrapped { public static void main(String[] args) { int a[] = { 2, 3, 5, 1, 4, 7, 10, 8, 11, 12, 1, 5, 7, 9, 2 }; System.out.println("Total Water Trapped is :" + totalWaterTrapped(a)); int a1[] = { 7, 1, 4, 0, 2, 8, 6, 3, 5 }; System.out.println("Total Water Trapped is :" + totalWaterTrapped(a1)); } public static int totalWaterTrapped(int a[]) { int sum = 0; int p1 = 0; int p2 = a.length - 1; int maxLeft = a[p1]; int maxRight = a[p2]; int minRightNow = Math.min(maxLeft, maxRight); boolean moveLeftPointer = maxLeft <= maxRight; // Here we are moving min value pointer. while (p1 != p2) { if (moveLeftPointer) { p1++; if (a[p1] > minRightNow) { maxLeft = a[p1]; minRightNow = Math.min(maxLeft, maxRight); } else { sum += minRightNow - a[p1]; } } else { p2--; if (a[p2] > minRightNow) { maxRight = a[p2]; minRightNow = Math.min(maxLeft, maxRight); } else { sum += minRightNow - a[p2]; } } moveLeftPointer = maxLeft <= maxRight; // Moving pointer which has min value. } return sum; } } // Get more details about this solution in below videos // https://www.youtube.com/watch?v=pq7Xon_VXeU&t=445s |