add some more array and strings solutions

Author: beck chen

leetcode practice/array and strings/groupAnagrams.js

@@ -0,0 +1,9 @@
+var groupAnagrams = function (strs) {
+    const wordMap = {};
+    strs.forEach(str => {
+        const sortedStr = str.split('').sort().join();
+        wordMap[sortedStr] = wordMap[sortedStr] === undefined ? [str] : [...wordMap[sortedStr], str];
+    })
+
+    return Object.values(wordMap)
+};

leetcode practice/array and strings/setMatrixZeros.js

@@ -0,0 +1,42 @@
+/**
+ * @param {number[][]} matrix
+ * @return {void} Do not return anything, modify matrix in-place instead.
+ */
+var setZeroes = function (matrix) {
+    const numRows = matrix.length;
+    const numColumns = matrix[0].length;
+    let firstColHasZero = false;
+
+    for (let rowIndex = 0; rowIndex < numRows; rowIndex++) {
+        if (matrix[rowIndex][0] === 0) {
+            firstColHasZero = true;
+        }
+
+        for (let colIndex = 1; colIndex < numColumns; colIndex++) {
+            if (matrix[rowIndex][colIndex] === 0) {
+                matrix[0][colIndex] = 0;
+                matrix[rowIndex][0] = 0;
+            }
+        }
+    }
+
+    for (let rowIndex = 1; rowIndex < numRows; rowIndex++) {
+        for (let colIndex = 1; colIndex < numColumns; colIndex++) {
+            if (matrix[rowIndex][0] === 0 || matrix[0][colIndex] === 0) {
+                matrix[rowIndex][colIndex] = 0;
+            }
+        }
+    }
+
+    if (matrix[0][0] === 0) {
+        for (let colIndex = 0; colIndex < numColumns; colIndex++) {
+            matrix[0][colIndex] = 0;
+        }
+    }
+
+    if (firstColHasZero) {
+        for (let rowIndex = 0; rowIndex < numRows; rowIndex++) {
+            matrix[rowIndex][0] = 0;
+        }
+    }
+};

leetcode practice/array and strings/trappingRainwater.js

@@ -0,0 +1,24 @@
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var trap = function (bars) {
+    if (!bars || bars.length === 0) { return null; }
+
+    const stack = [];
+    let globalVolume = 0;
+    for (let barIndex = 0; barIndex < bars.length; barIndex++) {
+        while (stack.length !== 0 && bars[barIndex] > bars[stack[stack.length - 1]]) {
+            const shortBarIndex = stack.pop();
+            if (stack.length === 0) { break; }
+            const lastPeakIndex = stack[stack.length - 1];
+            const numberOfBars = barIndex - lastPeakIndex - 1;
+            const heightDifference = Math.min(bars[barIndex], bars[lastPeakIndex]) - bars[shortBarIndex];
+            globalVolume += heightDifference * numberOfBars;
+        }
+
+        stack.push(barIndex);
+    }
+
+    return globalVolume;
+};