solution.ts

function maxWidthRamp (A: number[]): number {
    const stack = [0, ];
    for (let i = 1; i < A.length; i++) {
        if (A[i] < A[stack[stack.length - 1]]) {
            stack.push(i);
        }
    }
    let result = 0;
    for (let i = A.length - 1; i > 0; i--) {
        while (stack.length && stack[stack.length - 1] >= i) {
            stack.pop();
        }
        while (stack.length && A[stack[stack.length - 1]] <= A[i]) {
            result = Math.max(result, i - stack.pop()!);
        }
    }
    return result;
}


function maxWidthRamp2(nums: number[]): number {
    const stack:number[] = [];
    let result = 0;
    for(let i=0;i<nums.length;i++){
        if(stack.length === 0 || nums[i]<nums[stack[stack.length-1]] ){
            stack.push(i);
        }
    }
    for(let i=nums.length-1;i>-1 && stack.length>0;i--){
        while(stack.length && nums[stack[stack.length-1]]<=nums[i] ){
            const index = stack.pop()!;
            result = Math.max(result,i-index);
        }
    }
    return result
};