84-Largest-Rectangle-in-Histogram

Author: mariegobran

javascript/84-Largest-Rectangle-in-Histogram.js

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+/**
+ * @param {number[]} heights
+ * @return {number}
+ */
+ var largestRectangleArea = function(heights) {
+    let largestArea = 0;
+    let stack = [];
+    
+    for (let i = 0; i< heights.length; i++){
+        let start = i;
+        
+        while ( stack.length > 0 && stack[stack.length-1][1] > heights[i] ){
+            let [lastI, lastH] = stack.pop();
+            largestArea = Math.max(largestArea, lastH * (i-lastI));
+            start = lastI;
+        }
+        
+        stack.push([ start, heights[i] ]);
+    }
+    
+    for (let j = 0; j < stack.length; j++){
+        let currArea = stack[j][1] * (heights.length - stack[j][0]);
+        largestArea = Math.max(largestArea, currArea);
+    }
+    
+    return largestArea;
+};