AC!

2023203/main.cpp

@@ -1,84 +1,48 @@
 #include <stdio.h>
-#define RISING true
-#define FALLING false
+// 创建一个栈，拿到一个数，与栈顶比较，如果比栈顶小，压栈（正在波峰向波谷下降）
+// 比栈顶大
 
-unsigned long long totalCount;
-int peakValleyPos[10000];
-int powers[100000];
+struct NumberNode {
+    int data;
+    int count;
+};
 
-void find_pairs(int startPeakNum, int endPeakNum) {
-    if (startPeakNum + 2 == endPeakNum) {
-        totalCount +=
-            (peakValleyPos[endPeakNum] - peakValleyPos[startPeakNum + 1]) *
-            (peakValleyPos[startPeakNum + 1] - peakValleyPos[startPeakNum]) - 1;
-        return;
-    }
 
-    int maxInsidePeak = startPeakNum + 2;
-    int i = maxInsidePeak + 2;
-    while (i < endPeakNum) {
-        if (powers[i] > powers[peakValleyPos[maxInsidePeak]]) {
-            maxInsidePeak = i;
-        }
-        i += 2;
-    }
-
-    int countLeft = 0, countRight = 0;
-    i = startPeakNum;
-    while (powers[i] >= powers[peakValleyPos[maxInsidePeak]]) {
-        countLeft++;
-        i++;
-    }
-
-    i = endPeakNum;
-    while (peakValleyPos[i] >= powers[peakValleyPos[maxInsidePeak]]) {
-        countRight++;
-        i--;
-    }
-
-    totalCount += countLeft * countRight;
-    
-    find_pairs(startPeakNum, maxInsidePeak);
-    find_pairs(maxInsidePeak, endPeakNum);
-}
+long long totalPairs;
+NumberNode powers[500010];
 
 int main() {
+    int len = 1;
     int N;
-    int newPeakValleyPosIndex = 1;
-    bool direction = FALLING;
-    int firstPeakPos = 0, lastPeakPos = 0;
-    
-    peakValleyPos[0] = 0;
+    int input;
+    totalPairs = 0;
+    powers[0].data = 0;
+    powers[0].count = 0;
     scanf("%d", &N);
-    scanf("%d", &powers[0]);
-    scanf("%d", &powers[1]);
-    if (powers[0] < powers[1]) {
-        direction = RISING;
-        firstPeakPos = 1;
-    }
-    for (int i = 2; i < N; i++) {
-        scanf("%d", &powers[i]);
-        if (powers[i] > powers[i - 1] && direction == FALLING) {
-            peakValleyPos[newPeakValleyPosIndex++] = i - 1;
-            direction = RISING;
+    scanf("%d", &powers[1].data);
+    powers[1].count = 1;
+    N--;
+    for (int i = 0; i < N; i++) {
+        scanf("%d", &input);
+        while (len != 0 && powers[len].data < input) {
+            totalPairs += powers[len].count;
+            len--;
         }
-        else if (powers[i] < powers[i - 1] && direction == RISING) {
-            peakValleyPos[newPeakValleyPosIndex++] = i - 1;
-            direction = FALLING;
+        if (len == 0 ) {
+            powers[1].data = input;
+            powers[1].count = 1;
+            len = 1;
+        } else {
+            if (powers[len].data == input) {
+                totalPairs += powers[len].count + (len > 1);
+                powers[len].count++;
+            }
+            else  {
+                totalPairs += 1;
+                powers[++len] = NumberNode {input, 1};
+            }
         }
     }
-
-    if (direction == RISING) {
-        peakValleyPos[newPeakValleyPosIndex] = N - 1;
-        lastPeakPos = newPeakValleyPosIndex;
-    }
-    else {
-        lastPeakPos = newPeakValleyPosIndex - 1;
-    }
-
-    find_pairs(firstPeakPos, lastPeakPos);
-
-    totalCount += N - 1;
-    printf("%lld", totalCount);
-
+    printf("%lld", totalPairs);
+    return 0;
 }