【牛客网】构造MaxTree

来源：互联网发布：mac打印6寸相纸编辑：程序博客网时间：2024/06/07 01:06
#include <iostream>#include <cstdio>#include <cstring>#include <vector>#include <stack>#include <algorithm>using namespace std;class MaxTree {public:    vector<int> buildMaxTree(vector<int> A, int n) {            const int NONE = -1;            vector<int> left; //下标            vector<int> right;//下标            stack<int> myStack;//下标            int Size = A.size();            myStack.push(0);            left.push_back(NONE);            for(int i = 1; i < Size; i++) {                int topValue = A[myStack.top()];                while(!myStack.empty() && A[i] > topValue) {                        myStack.pop();                        if(myStack.empty()) break;//省略数组越界异常！                        topValue = A[myStack.top()];                }                if(myStack.empty()) {                        left.push_back(NONE);                        myStack.push(i);                } else {                        left.push_back(myStack.top());                        myStack.push(i);                }            }            while(!myStack.empty()) {                myStack.pop();            }            myStack.push(Size-1);            right.push_back(NONE);            for(int i = Size-2; i >= 0; i--) {                int topValue = A[myStack.top()];                while(!myStack.empty() && A[i] > topValue) {                        myStack.pop();                        if(myStack.empty()) break;                        topValue = A[myStack.top()];                }                if(myStack.empty()) {                        right.push_back(NONE);                        myStack.push(i);                } else {                        right.push_back(myStack.top());                        myStack.push(i);                }            }            reverse(right.begin(), right.end());            vector<int> result;            for(int i = 0; i < Size; i++) {                if(left[i] == NONE && right[i] == NONE) {                        result.push_back(-1);                } else if((left[i] == NONE && right[i] != NONE) || (left[i] != NONE && right[i] == NONE) ) {                        if(left[i] != NONE) result.push_back(left[i]);                        else result.push_back(right[i]);                } else {                        if(A[left[i]] > A[right[i]]) result.push_back(right[i]);                        else result.push_back(left[i]);                }            }            return result;    }};int main(){    vector<int> A;    int n;    int input;    while(scanf("%d", &n) != EOF) {        A.clear();        for(int i = 0; i < n; i++) {                scanf("%d", &input);                A.push_back(input);        }         MaxTree *obj = new MaxTree();         vector<int> result = obj->buildMaxTree(A, n);         cout << "result: ";         for(int i = 0; i < (int)result.size(); i++) {           printf("%d  ", result[i]);        }    }    return 0;}/***108 1 9 3 2 6 0 5 4 7***/
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