标签：style blog io ar color os sp for on
一． 题意
给出5个数和4则运算，看能不能算出目标值出来，如果算不出来就算出比目标值小的最大值。深搜：每一步选两个数做运算，然后算出的结果作为下一步的其中一个操作数。每一步选数有C(5,2)种，每两个数间又有5种运算结果（减法位置不同算两种）。
二． 做法：
用数组存储放进来的5各操作数，并在这个过程中用来存放中间答案，没进行一次计算操作数的个数就会减少一个。注意每一步深搜之后都要恢复原本状态。
三． 源码
1 // 2 // main.cpp 3 // sicily-1050 4 // 5 // Created by ashley on 14-10-10. 6 // Copyright (c) 2014年 ashley. All rights reserved. 7 // 8 9 #include <iostream> 10 using namespace std; 11 int storing[5]; 12 int answer, result; 13 void depthSearch(int size) 14 { 15 for (int i = 0; i < size; i++) { 16 if (storing[i] > result && storing[i] <= answer) { 17 result = storing[i]; 18 } 19 } 20 if (result == answer) { 21 return; 22 } 23 if (size == 1) { 24 return; 25 } 26 for (int i = 0; i < size - 1; i++) { 27 for (int j = i + 1; j < size; j++) { 28 int left, right; 29 left = storing[i]; 30 right = storing[j]; 31 storing[j] = storing[size - 1]; 32 //add and decrease a number 33 storing[i] = left + right; 34 depthSearch(size - 1); 35 //subtract and decrease a number 36 storing[i] = left - right; 37 depthSearch(size - 1); 38 //subtract and decrease a number 39 storing[i] = right - left; 40 depthSearch(size - 1); 41 //multiply and decrease a number 42 storing[i] = left * right; 43 depthSearch(size - 1); 44 //divide and decrease a number 45 if (left != 0 && right % left == 0) { 46 storing[i] = right / left; 47 depthSearch(size - 1); 48 } 49 if (right != 0 && left % right == 0) { 50 storing[i] = left / right; 51 depthSearch(size - 1); 52 } 53 storing[i] = left; 54 storing[j] = right; 55 } 56 } 57 } 58 int main(int argc, const char * argv[]) 59 { 60 int runs; 61 cin >> runs; 62 while (runs--) { 63 for (int i = 0; i < 5; i++) { 64 cin >> storing[i]; 65 } 66 cin >> answer; 67 result = -101; 68 depthSearch(5); 69 cout << result << endl; 70 } 71 return 0; 72 }
标签：style blog io ar color os sp for on
原文地址：http://www.cnblogs.com/ashley-/p/4151813.html
