add peakFinding1D.js

Author: jiangweixu

peakFinding1D.js

@@ -0,0 +1,60 @@
+/*
+* 查找峰值，一位数组的情况下。定义峰值a[i]，满足a[i]>a[i-1], a[i]>a[i+1].
+* */
+
+/*
+* 1、二分查找，复杂度O(logn)
+* */
+function peakFinding1D (arr) {
+    var l = arr.length, mid = Math.floor(l/2);
+
+    switch (true) {
+        case l === 1:
+            return arr[0];
+            break;
+        case l === 2:
+            return arr[0] > arr[1] ? arr[0] : arr[1];
+            break;
+        default:
+            break;
+    }
+
+    if (arr[mid] < arr[mid + 1]) {
+        return peakFinding1D(arr.slice(mid, l));
+    }
+    if (arr[mid] < arr[mid - 1]) {
+        return peakFinding1D(arr.slice(0, mid))
+    }
+    return arr[mid];
+}
+
+
+/*
+* 2、原始暴利检索
+* */
+function peakFinding1DBrutSearch (arr) {
+    var l = arr.length;
+    if (l === 1) {
+        return arr[0];
+    }
+    for (var i = 0; i < l; i++) {
+        if (i === 0 && arr[i] > arr[i+1]) {
+            return arr[i];
+        }
+        if (i === l - 1 && arr[i] > arr[i-1]) {
+            return arr[i];
+        }
+        if (arr[i] > arr[i-1] && arr[i] > arr[i+1]) {
+            return arr[i];
+        }
+    }
+}
+
+
+function getArr(n) {
+    var n = n || 20000, i = 0, arr = [];
+    while(i < n) {
+        arr[i++] = Math.floor(Math.random()*100);
+    }
+    return arr;
+}