leetcode 第五天

2018年1月6日

22.(566) Reshape the Matrix

JAVA

class Solution {    public int[][] matrixReshape(int[][] nums, int r, int c) {        int[][] newNums = new int[r][c];        int size = nums.length*nums[0].length;        if(r*c != size)            return nums;        for(int i=0;i

23.(268) Missing Number

JAVA

class Solution {    /*数列求和思想*/    public int missingNumber(int[] nums) {        int expectSum = nums.length*(nums.length+1)/2;        int actualSum = 0;        for(int num : nums) actualSum += num;        return expectSum - actualSum;    }}

24.(243) ==Shortest Word Distance==

JAVA

class Solution {    public int shortestDistance(String[] words,String word1,String word2) {        int idx1 = -1,idx2 = -1;        int minDistance = words.length;        int currentDistance;        for(int i =0;i

25.(561) Array Partition I

JAVA

class Solution {    public int arrayPairSum(int[] nums) {        Arrays.sort(nums);        int minSum = 0;        for(int i = 0;i

26.(746) ==Min Cost Climbing Stairs==

==新知识点：动态规划（有点难度）==

JAVA

class Solution {    public int minCostClimbingStairs(int[] cost) {        int f1=0;        int f2=0;        int f3=0;//f3为到达每一个楼层所需要花费的最小钱数(此楼层花费不算)        for(int i = 2;i <= cost.length;i++){            f3 = Math.min(f1+cost[i-2],f2+cost[i-1]);            f1 = f2;            f2 = f3;        }        return f3;    }}

27.(724) Find Pivot Index

JAVA

class Solution {    public int pivotIndex(int[] nums) {        int sum = 0,leftSum = 0;        for(int num : nums) sum+=num;        for(int i = 0;i < nums.length;i++){            if(leftSum == sum - leftSum - nums[i])                return i;            leftSum += nums[i];        }        return -1;            }}

28.(66) Plus One

JAVA

class Solution {    public int[] plusOne(int[] digits) {        int n = digits.length;        for(int i = n-1;i>=0;i--){            if(digits[i]<9){                digits[i]++;                return digits;            }            digits[i] = 0;        }        //此处是为了防止原始数字为999...的情况        int[] result = new int[n+1];        result[0] = 1;        return result;    }}

29.(1) Two Sum

==注意Map/HashMap的声明、get()/containsKey()/put()等操作==

JAVA

class Solution {    public int[] twoSum(int[] nums, int target) {        Map
    
      map = new HashMap
     
      ();        int[] result;        for(int i = 0;i